Jean-Baptiste Berthelin

Brigitte Grau

Martine Hurault-Plantet

Two levels of evaluation in a complex NL system

The QALC question-answering system, developed at LIMSI, has been a participant for two years in the QA track of the TREC conference. In this paper, we present a quantitative evaluation of various modules in our system, based on two criteria: first, the numbers of documents containing the correct answer and selected by the system; secondly, the number of answers found. The first criterion is used for evaluating locally the modules in the system, which contribute in selecting documents that are likely to contain the answer. The second one provides a global evaluation of the system. As such, it also serves for an indirect evaluation of various modules.

Introduction

For two years, the TREC Evaluation Conference, (Text REtrieval Conference) has been featuring a Question Answering track, in addition to those already existing. This track involves searching for answers to a list of questions, within a collection of documents provided by NIST, the conference organizer. Questions are factual or encyclopaedic, while documents are newspaper articles. The TREC9-QA track, for instance, proposed 700 questions whose answers should be retrieved in a corpus of about one million documents.

In addition to the evaluation, by human judges, of their systemsÕ results [START_REF] Voorhees | Implementing a Question Answering Evaluation[END_REF], TREC participants are also provided with an automated evaluation tool, along with a database. These data consist of a list of judgements of all results sent in by all participants. The evaluation tool automatically delivers a score to a set of answers given by a system to a set of questions. This score is derived from the mean reciprocal rank of the first five answers. For each question, the first correct answers get a mark in reverse proportion to their rank. Those evaluation tool and data are quite useful, since it gives us a way of appreciating what happens when modifying our system to improve it.

We have been taking part to TREC for two years, with the QALC question-answering system [START_REF] Ferret | QALC Ñ the Question-Answering system of LIMSI-CNRS[END_REF], currently developed at LIMSI. This system has following architecture: parsing of the question to find the expected type of the answer, selection of a subset of documents among the approximately one million TREC-provided items, tagging of named entities within the documents, and, finally, search for possible answers. Some of the components serve to enrich both questions and documents, by adding system-readable data into them. Such is the case for the modules that parse questions and tag documents. Other components operate a selection among documents, using added data. One example of such modules are those which select relevant documents, another is the one which extracts the answer from the documents.

A global evaluation of the system is based on judgement about its answers. This criterion provides only indirect evaluation of each component, via the evolution of the final score when this component is modified. To get a closer evaluation of our modules, we need other criteria. In particular, concerning the evaluation of components for document selection, we adopted an additional criterion about selected relevant documents, that is, those that yield the correct answer.

This paper describes a quantitative evaluation of various modules in our system, based on two criteria: first, the number of selected relevant documents, and secondly, the number of found answers. The first criterion is used for evaluating locally the modules in the system, which contribute in selecting documents that are likely to contain the answer. The second one provides a global evaluation of the system. It also serves for an indirect evaluation of various modules.

System architecture

Figure 1 shows the architecture of the QALC system, made of five separate modules: Question analysis, Search engine, Re-indexing and selection of documents, Named entity recognition, and Question/sentence pairing.

Selection of relevant documents

The second module is a classic search engine, giving, for each question, a ranked list of documents, each of which could contain the answer.

This set of documents is then processed by a third module, made of FASTR [START_REF] Jacquemin | Syntagmatic and paradigmatic representations of term variation[END_REF], a shallow transformational natural language analyser and of a ranker. This module can select, among documents found by the search engine, a subset that satisfies more refined criteria. FASTR improves things because it indexes documents with a set of terms, including not only the (simple or compound) words of the initial question, but also their morphological, syntactic and semantic variants. Each index is given a weight all the higher as it is close to the original word in the question, or as it is significant. For instance, original terms are considered more reliable than semantic variants, and proper names are considered more significant than nouns. Then, documents are ordered according to the number and the quality of the terms they contain. An analysis of the weight graph of the indexed documents enables the system to select a relevant subpart of those documents, whose size varies along the questions. Thus, when the curve presents a high negative slope, the system only select documents before the fall, otherwise a fixed threshold is used.

Named entity recognition

The fourth module tags named entities in documents selected by the third one. Named entities are recognized through a combination of lexico-syntactic patterns and significantly large lexical data. The three lists used for lexical lookup are CELEX (1998), a lexicon of 160,595 inflected words with associated lemma and syntactic category, a list of 8,070 first names (6,763 of which are from the CLR (1998) archive) and a list of 211,587 family names also from the CLR archive.

Question-sentence pairing

The fifth module evaluates each sentence in the ranker-selected documents, using a similarity measure between, on one side, terms and named entities in the sentence, and on the other side, words in the questions and expected answer type. To do so, it uses the results of the question parser, and the named entity tagger, along with a frequency-weighted vocabulary of the TREC corpus.

The QALC system proposes long and short answers. Concerning the short ones, the system focuses on parts of sentences that contain the expected named entity tags, when they are available, or on the larger subpart without any terms.

Search engine evaluation

The second module of the QALC system deals with the selection, through a search engine, of documents that may contain an answer to a given question from the whole TREC corpus (whose size is about 3 gigabytes).

We tested three search engines with the 200 questions that were proposed at the TREC8 QA track. The first one is Zprise, a vectorial search engine developed by NIST. The second is Indexal (de Loupy et al 1998), a pseudo-boolean search engine developed by Bertin Technologies 1 . The third search engine is ATT whose results to the TREC questions are provided by NIST in the form of ranked lists of the top 1000 documents retrieved for each question. We based our search engine tests on 1 We are grateful to Bertin Technologies for providing us with the outputs of Indexal on the TREC collection for the TREC8-QA and TREC9-QA question set.

the list of relevant documents extracted from the list of correct answers provided by TREC organizers.

Since a search engine produces a large ranked list of relevant documents, we had to define the number of documents to retain for further processing. Indeed, having too many documents leads to a question processing time that is too long, but conversely, having too few documents reduces the possibility of obtaining the correct answer. The other goal of the tests obviously was to determine the best search engine, that is to say the one that gives the highest number of relevant documents.

Document selection threshold

In order to determine the best selection threshold, we carried out four different tests with the Zprise search engine. We ran Zprise for the 200 questions and then compared the number of relevant documents respectively in the top 50, 100, 200, and 500 retrieved documents. 1, the improvement of the search engine results tends to decrease beyond the threshold of 200 documents. The top 200 ranked documents thus seem to offer the best trade-off between the number of documents in which the answer may be found and the question processing time.

Evaluation

We compared the results given by the three search engines for a threshold of 200 documents. All three search engines perform quite well. Nevertheless, the ATT search engine revealed itself the most efficient according to the following two criteria: the lowest number of questions for which no relevant document was retrieved, and the most relevant documents retrieved for all the 200 questions. Both criteria are important. First, it is most essential to obtain relevant documents for as many questions as possible. But the number of relevant documents for each question also counts, since having more sentences containing the answer implies a greater probability to actually find it.

Document ranking evaluation

As the processing of 200 documents by the following Natural Language Processing (NLP) modules still was too time-consuming, we needed an additional stronger selection. The selection of relevant documents performed by the re-indexing and selection module relies on an NLP-based indexing composed of both single-word and phrase indices, and linguistic links between the occurrences and the original terms. The original terms are extracted from the questions. The tool used for extracting text sequences that correspond to occurrences or variants of these terms is FASTR [START_REF] Jacquemin | Syntagmatic and paradigmatic representations of term variation[END_REF]. The ranking of the documents relies on a weighted combination of the terms and variants extracted from the documents. The use of multiwords and variants for document weighting makes a finer ranking possible.

The principle of the selection is the following: when there is a sharp drop of the documents weight curve after a given rank, we keep only those documents which occur before the drop. Otherwise, we arbitrarily keep the first 100.

In order to evaluate the efficiency of the ranking process, we proceeded to several measures. First, we apply our system on the material given for the TREC8 evaluation, one time with the ranking process, and another time without this process. 200 documents were retained for each of the 200 questions. The system was scored by 0.463 in the first case, and by 0.452 in the second case. These results show that document selection slightly improves the final score while much reducing the amount of text to process.

However, a second measurement gave us more details about how things are improved. Indeed, when we compare the list of relevant documents selected by the search engine with the list of ranker-selected ones, we find that the ranker loses relevant documents. For thirteen questions among the 200 in the test, the ranker did not consider relevant documents selected by the search engine. What happens is: the global score improves, because found answers rank higher, but the number of found answers remains the same.

The interest to perform such a selection is also illustrated by the results given Table 3 We see that the selection process discards documents for 50% of the questions: 340 questions are processed from less than 100 documents. For those 340 questions, the average number of selected documents is 37. The document set retrieved for those questions has a weight curve with a sharp drop. QALC finds more often the correct answer and in a better position for these 340 questions than for the 342 remaining ones. These results are very interesting when applying such time-consuming processes as named-entities recognition and question/sentence matching. Document selection will also enable us to apply further sentence syntactic analysis.

Question-sentence pairing evaluation

We sent to TREC9 two runs which gave answers of 250 characters length, and one run which gave answers of 50 characters length. The first and the last runs used ATT as search engine, and the second one, Indexal. Results are consistent with our previous analysis (see Section 3.2). Indeed, the run with ATT search engine gives slightly better results (0.407 strict) 2 than those obtained with the Indexal search engine (0.375 strict). The score of the run with answers of 50 characters length was not encouraging, amounting only 0.178, with 183 correct answers retrieved 3 .

Long answers

From results of the evaluation concerning document ranking, we see that the performance level of the question-sentence matcher depends partly on the set of sentences it has parsed, and not only on the presence, or absence, of the answer within these sentences. In other words, we do not find the answer each time it is in the set of selected sentences, but we find it easily if there are few documents (and then few sentences) selected. That is because similarity 2 With this score, the QALC system was ranked 6th among 25 participants at TREC9 QA task for answers with 250 characters length. 3 With this score, the QALC system was ranked 19th among 24 participants at TREC9 QA task for answers with 50 characters length. assessment relies upon a small number of criteria, which are found to be insufficiently discriminant. Therefore, several sentences obtain the same mark, in which case, the rank of the correct answer depends on the order in which sentences are encountered. This is something we cannot yet manage, so we evaluated the matcherÕs performance, without any regard to the side effect induced by document processing order. As remarked in 3.2, search engines perform well. In particular, ATT retains relevant documents, namely, those that yield good answers, for 97 percent of the questions. The ranker, while improving the final score, loses some questions. After it stepped in, the system retains relevant documents for 90% of the questions. The matcher finds a relevant document in the first five answers for 74% of the questions, but answers only 62% of them correctly. Finding the right document is but one step, knowing where to look inside it is no obvious task.

Short answers

A short answer is selectively extracted from a long one. We submitted this short answer selector (under 50 characters) to evaluation looking for the impact of the expected answer type. Among TREC questions, some expect an answer consisting of a named entity: for instance a date, a personal or business name. In such cases, assigning a type to the answer is rather simple, although it implies the need of a good named entity recognizer. Answers to other questions (why questions for instance, or some sort of what questions), however, will consist of a noun or sentence. Finding its type is more complex, and is not done very often. Some systems, like FALCON [START_REF] Harabagiu | Experiments with Open-Domain Textual Question Answering[END_REF] use Wordnet word class hierarchies to assign types to answers. Among 682 answers in TREC9, 57.5% were analysed by our system as named-entity questions, while others received no type assignment. Among answers from our best 250-character run, 62.7% were about named entities. However, our run for shorter answers, yielding a more modest score, gives 84% of named-entities answers. In our system answer type assignment is of surprisingly small import, where longer answers are concerned. However, it does modify the selecting process, when the answer is extracted from a longer sentence.

Such evaluations help us to see more clearly where our next efforts should be directed. Having more criteria in the similarity measurement would, in particular, be a source of improvement.

Discussion

We presented quantitative evaluations. But since we feel that evaluations should contribute to improvements of the system, more qualitative and local ones also appear interesting.

TREC organizers send us, along with run results, statistics about how many runs found the correct answer, and at which rank. Such statistics are useful in many ways. Particularly, they provide a characterisation of a posteriori difficult questions. Knowing that a question is a difficult one is certainly relevant when trying to answer it. Concerning this problem, de [START_REF] De Loupy | Evaluation of Document Retrieval Systems and Query Difficulty[END_REF] proposed an interesting set of criteria to recognize a priori difficult questions. They use word frequency, multi-words, polysemy (a source of noise) and synonymy (a source of silence). They argue that an ÒintelligentÓ system could even insist that a question be rephrased when it is too difficult. While their approach is indeed quite promising, we consider that their notion of a priori difficulty should be complemented by the notion of a posteriori difficulty we mentioned: the two upcoming examples of queries show that a question may seem harmless at first sight, even using de Loupy and BellotÕs criteria, and still create problems for most systems.

From these statistics, we also found disparities between our system and others for certain questions. At times, it finds a good answer where most others fail and obviously the reverse also happens. This is the case in the two following examples. The first one concerns an interesting issue in a QA system that is the determination of which terms from the question are to be selected for the question-answer pairing. This is particularly important when the question has few words. For instance, to the question How far away is the moon?, our term extractor kept not only moonÊ(NN), but also awayÊ(RB). Moreover, our question parser knows that how far is an interrogative phrase yielding a LENGTH type for the answer. This leads our system to retrieve the correct answer: With a 28-power telescope, you can see it on the moon 250,000 miles away4 .

The second example concerns the relative weight of the terms within the question. When a proper noun is present, it must be found in the answer, hence an important weight for it. Look at the question Who manufactures the software, ÇÊPhotoShopÊÈ?. The term extractor kept s o f t w a r e ( N N ) , PhotoShop(NP), a n d manufacture(VBZ) as terms to be matched, but the matcher assigns equal weights to them, so we could not find the answer5 . Later, we modified these weights, and the problem was solved.

Indeed, evaluation corpus seems to be difficult to build. Apart from the problem of the question difficulty level, question type distribution may also vary from a corpus to another. For instance, we note that TREC8 proposed much more questions with named entity answer type (about 80%) than TREC9 (about 60%). Thus, some participants who trains their systems on the TREC8 corpus were somehow disapointed by their results at TREC9 with regards with their training results [START_REF] Scott | University of Sheffield TREC-9 Q & A System[END_REF].

However, it is generally hard to predict what will happen if we modify the system. A local improvement can result in a loss of performance for other contexts. Although the systemÕs complexity cannot be reduced to just two levels (a local one and a global one), this can be an efficient step in the design of improvements to the whole system via local adjustments. But this is a very frequent situation in engineering tasks.

Conclusion and perspectives

Each evaluation reflects a viewpoint, underlying the criterion we use. In our case, the choice of criteria was guided by the existence of two main stages in the QA process, namely the selection of relevant documents and the selection of the answer among the selected documents sentences. Sometimes, such criteria concur in revealing the same positive or negative feature of the system. They can also yield a more precise assessment of the reasons behind these features, as was the case in our evaluation of the ranker. Moreover, when a system consists of several modules, their specific evaluations should imply different criteria. This is particularly true in dialogue systems, where different kinds of processes are cooperating. Since information retrieval is an interactive task, it seems natural to associate a dialogue component to it. Indeed, users tend to ask a question, evaluate the answer, and reformulate their question to make it more specific (or, contrariwise, more general, or quite different). A QA system is, therefore, a good applicative setting for a dialogue module. Quantitative assessment of the QA system would be useful in assessing the dialogue system in this particular context. Such a global assessment would provide an objective judgement about whether the task (finding the answer) was achieved, or not. Successfulness in a task is a necessary component of the evaluation, nevertheless it is just a part of it. Obviously, dialogue evaluation is also a matter of cost (time, number of exchanges) and of userfriendliness (cognitive ergonomy).

However, objectivity is almost impossible to attain in these domains. In a recent debate (LREC 2000), serious objections about natural language tools evaluation and validation were developed e.g. by [START_REF] Sabah | To validate or not to validate? Some theoretical difficulties for a scientific evaluation of natural language processing systems[END_REF]. The main issue he raises is about the great complexity of such systems. However, we consider that by going as far as possible in the experimental search for evaluation criteria, we also make a meaningful contribution to this debate. While it is true that complexity should never be ignored, we consider that, by successive approximate modelisation and evaluation cycles, we can capture some of it at each step of our systemÕs developement.

  Table 1 shows the test results.

	Selection Threshold	Questions with relevant	Questions with no relevant
		documents	documents
	50	181	19
	100	184	16
	200	193	7
	500	194	6
	Table 1. Number of questions with and
	without relevant documents retrieved for
		different thresholds
	According to Table

Table 2 .

 2 Table 2 gives the tests results. Compared performances of the Indexal, Zprise and ATT search engines

	Search Engine	Indexal Zprise ATT
	Number of questions
	with relevant	182	193	194
	documents retrieved
	Number of questions
	without relevant	18	7	6
	documents retrieved
	Total number of
	relevant documents	814	931	1021
	that were retrieved

  , computed on the TREC9 results.

	Number of documents	100	<<100
	selected by ranking
	Distribution among the	342	340
	questions	(50%)	(50%)
	Number of correct	175	200
	answers	(51%)	(59%)
	Number of correct answer	88	128
	at rank 1	(50%)	(64%)

Table 3 .

 3 Evaluation of the ranking process

Table 4 .

 4 Table 4 sums up the number of answers found by our two runs. Number of correct answers retrieved, by rank, for the two runs at 250 characters

	Rank of the correct	Run using	Run using
	answer retrieved	ATT	Indexal
	1	216	187
	2 to 5	159	185
	Total of correct answers retrieved	375	372
	No correct answer retrieved	307	310

Among the 42 runs using 250 byte limit, submitted at TREC9-QA, only seven found the correct answer at rank 1, and 27 do not found it.

22 runs, out of 42 found the right answer at rank 1. Only 9 were unable to find it.


Yu I Kantor
email: kantor@malaco-sevin.msk.ru

N Puillandre
email: puillandre@mnhn.fr

B M Olivera

P Bouchet
email: pbouchet@mnhn.fr

A N Severtzov

Morphological proxies for taxonomic decision in turrids (Mollusca, Neogastropoda): a test of the value of shell and radula characters using molecular data

Keywords: shell, radula, COI, 28S, convergence, new species. Running head: Morphological proxies for taxonomic decision in turrids

The state of the art of turrid (= Turridae s.l.) systematics is that shells -when it includes the protoconch -are reliable species-level identifiers, but inadequate proxies for allocation to genera or subfamilies. Generally, the radula is used for allocation to a (sub)family, but the hypothesis that the radula is a more adequate proxy than the shell for relationships has not yet been tested by molecular data. Species of Xenuroturris may have drastically different radulae, with either "semi-enrolled" or "duplex" marginal teeth, although their shells are very similar or even almost indistinguishable. Molecular data confirm that specimens with different types of radulae constitute different species, but two species of a pair with respectively "semi-enrolled" and "duplex" teeth end up being not closely related. However, it is still unresolved whether species with "semi-enrolled" [= Iotyrris] and "duplex" teeth [= Xenuroturris] form two supported monophyletic clades. Iotyrris devoizei n.sp., and I. musivum n.sp., are described from Vanuatu, where they occur sympatrically with I. cingulifera and Xenuroturris legitima.

Introduction

Among the gastropod superfamily Conoidea, "Turridae" (sensu Powell, 1966) is the most speciose group of marine mollusks, with estimates of about 340 Recent valid genera and subgenera [START_REF] Taylor | Foregut anatomy, feeding mechanisms, relationships and classification of Conoidea (Toxoglossa) (Gastropoda)[END_REF] and 4,000 named living species [START_REF] Tucker | Catalog of Recent and fossil turrids (Mollusca: Gastropoda)[END_REF]. Tropical and deep-water faunas are reservoirs of vast numbers of undescribed species: [START_REF] Bouchet | An inordinate fondness for turrids. Molluscan Megadiversity: Sea, Land and Freshwater[END_REF] estimated that 58-72% of the 1,726 "turrid" species sampled in New Caledonia is undescribed, and the real number of Recent "turrid" species worldwide may be in the 10-20,000 species range. As is the case with other specialist predators, the vast majority of species occur in low abundance. As a result of a very large number of species and small number of specimens, turrid systematics is intimidating, and turrids are much less studied than other marine gastropods of comparable size. In the history of turrid systematics, shell, radula and anatomy have been given different value and emphasis at different taxonomical levels. Shells -when it includes the protoconch -are usually considered reliable species-level identifiers. However, convergence and homoplasy renders them much less reliable predictors of relationships at higher taxonomic levels (family, genus). For instance, shells of Toxicochlespira Sysoev and Kantor, 1990 (Conidae) strongly resemble representatives of Cochlespira Conrad, 1865 (Turridae) [START_REF] Sysoev | A new genus and species of "Cochlespira-like" turrids (Gastropoda, Toxoglossa, Turridae)[END_REF]; shells of Strictispira McLean, 1971 (Strictispiridae), are hardly distinguishable from those of many species of Crassispira Swainson, 1840 (Turrridae, Crassispirinae) [START_REF] Tippett | The genus Strictispira in the western Atlantic (Gastropoda: Conoidea)[END_REF]; and the radula-less species Cenodagreutes aethus Smith, 1967 is said to be conchologically indistinguishable from the radulate Raphitoma leufroyi (Michaud, 1828) (both Conidae, Raphitominae).

At higher taxonomic levels, anatomical characters, especially foregut anatomy, are used to define subfamilies and families [START_REF] Taylor | Foregut anatomy, feeding mechanisms, relationships and classification of Conoidea (Toxoglossa) (Gastropoda)[END_REF]. However, as these are accessed only after time consuming serial histological sectioning and reconstruction (e.g. [START_REF] Yui | Anatomical basis for the origin and evolution of toxoglossan mode of feeding[END_REF], the radula is routinely used as a proxy for the rest of foregut anatomy. Radulae have also the advantage that they can be extracted from animals with dried soft parts. Most of the currently recognized [START_REF] Taylor | Foregut anatomy, feeding mechanisms, relationships and classification of Conoidea (Toxoglossa) (Gastropoda)[END_REF] subfamilies within Turridae and Conidae were erected (e.g., [START_REF] Mclean | A revised classification of the family Turridae, with the proposal of new subfamilies, genera, and subgenera from the Eastern Pacific[END_REF], or subsequently redefined, on the basis of radular characters.

The state of the art of turrid systematics is thus based on the shell for species delimitation and/or identification, and on the radula for allocation to a (sub)family. These traditionally held beliefs were shattered when, during the course of routine radular preparations from New Caledonia "turrids", we found two distinct radular types in different specimens of what we initially classified as a single species, generally identified as Xenuroturris cingulifera [START_REF] Lamarck | Histoire naturelle des animaux sans vertèbres[END_REF], a species widely distributed in the Indo-Pacific [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF]). These differences in radulae would be considered to imply at least generic rank when applying conventional taxonomic decision, but in this case the specimens involved have shells so similar that they would hardly be separated as discrete morphs, and even less so as species, even by the most hardy conchologist. This prompted examination of radula and molecular characters of conchologically similar animals from the South and West Pacific, which resulted in evidence of further species "pairs" with similar shells and different radulae.

This is the first time such a case is reported in "turrids", and it brings new questions: is this an isolated case of radula polymorphism? Or is this a textbook case of shell convergence? A molecular analysis confirms that differences indicated by radulae are profound, but it does not rule out that similarities in shell morphologies are the result of conserved patterns rather than the result of convergence of evolved patterns.

Material and methods

Material for this study was collected over the course of several years during expeditions organized by the Muséum National d'Histoire Naturelle, Paris (MNHN) to New Caledonia (Expédition Montrouzier, 1993), the Loyalty Islands (LIFOU 2000), the Philippines (PANGLAO 2004), andVanuatu (SANTO 2006). Material for molecular studies was preserved in 90 or 100% ethanol by clipping pieces of the head-foot from anesthetized specimens. Radulae were extracted from the specimens (from those with dried bodies -after rehydration), cleaned with diluted bleach, rinsed in distilled water, mounted on the stubs, air dried, coated with a gold-palladium and investigated with a JEOL JSM 840A Scanning Microscope. Terminology and homology of the central teeth in Turrinae follows [START_REF] Yui | On the morphology and homology of the "central tooth" in the radulae of Turrinae (Conoidea: Turridae)[END_REF]. The following samples were examined in terms of radular morphology and also, where specifically mentioned, molecular sequences: Xenuroturris identified as "X. cingulifera" based on shell characters Specimens with "duplex" radular type [= Xenuroturris legitima Iredale, 1929] PHILIPPINES, Bohol Province, PANGLAO 2004, sta. G1, 09°41.9'N, 123°9,5'E, 100 m (2 spms -Fig. 2B-C). NEW CALEDONIA, Koumac, sta. 913, 20°58'S, 164°32'E, 10-13 m (1 spm -Fig. 2E), sta. 944, 20°35'S, 164°12'E, 14-15 m (1 spm -Fig. 2F). LOYALTY ISLANDS, LIFOU 2000, sta. 1465, 20°47.7'S, 167°07.0'E, 35-45 m (1 spm -Fig. 2D). ESPIRITU SANTO, VANUATU. SANTO 2006, sta. DR87, 15º38.5'S, 167º15.1'E, 13 m (1 specimen sequenced, MNHN 17684) (Fig. 2A,8A). Specimens with "semi-enrolled" radular type [= Iotyrris cingulifera Lamarck, 1822] NEW CALEDONIA, Nouméa, sta. 255, 22°25'S, 166°20'E, 11 m (1 spm); Nouméa, Grand Récif Aboré, 5 m (1 spm); Touho, sta. 1240 (Expedition Montrouzier), 20°46.5'S, 164°14'E, 0-2 m (1 spm -Fig. 3G); Koumac, sta. 941, 20°39'S, 164°13'E, 15-16 m (1 spm -Fig. 3F), sta. 1303 (Expedition Montrouzier), 20°37.7'S, 164°15.9'E, 0-8 m (1 spm -Fig. 3A 7A). Xenuroturris kingae [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF] NEW CALEDONIA. Koumac, sta. 1319 (Expedition Montrouzier), 20º44.1'S, 164º15.1'E, 15-20 m (2 specimens -Fig. 6 H-I, 8E).

Molecular study

Sequencing

DNA was extracted from a piece of foot, using 6100 Nucleic Acid Prepstation system (Applied Biosystem). A fragment of 658 bp of Cytochrome Oxydase I (COI) mitochondrial gene was amplified using the universal primers LCO1490 and HCO2198 developed by [START_REF] Folmer | DNA primers for amplification of mitochondrial cytochrome c oxidase subunit I from diverse metazoan invertebrates[END_REF]. One nuclear gene fragment was also analyzed: 900 bp of the rDNA 28S gene, involving D1, D2 and D3 domains [START_REF] Hassouna | The complete nucleotide sequence of mouse 28SrRNA gene. Implications for the process of size increase of the large subunit rRNA of higher eukaryotes[END_REF], using the primers C1 and D3 [START_REF] Jovelin | Phylogenetic relationships within the Polyopisthocotylean monogeneans (Plathyhelminthes) inferred from partial 28S rDNA sequences[END_REF]. All PCR reactions were performed in 25 µl, containing 3 ng of DNA, 1X reaction buffer, 2.5 mM MgCl 2 , 0.26 mM dNTP, 0.3 µM of each primer, 5% DMSO and 1.5 units of Q-Bio Taq (Qbiogene) for all genes. For 28S gene, termocycles consisted of an initial denaturation step at 94°C for 4', followed by 30 cycles of denaturation at 94°C for 30'', annealing at 52°C and extension at 72°C for 1'. The final extension was at 72°C for 10'. Thermocycles used for COI gene are described in [START_REF] Hebert | Biological identifications through DNA Barcodes[END_REF].

PCR products were purified and sequenced by the Genoscope, a French National Sequencing Center. Because of the length of the 28S PCR product, two internal primers (D2 and C2', [START_REF] Dayrat | New clades of Euthyneuran Gastropods (Mollusca) from 28S rRNA sequences[END_REF] were used for sequencing, in addition of primers used for PCR. All genes were sequenced for both directions to confirm accuracy of each sequences. Sequences were deposited in GenBank. Genbank accession numbers for corresponding specimens are provided in Tables 1 and2.

Phylogenetic Analyses

Three species of Turridae (each represented by a single specimen) were used as outgroups for phylogenetic analyses: Lophiotoma albina [START_REF] Lamarck | Histoire naturelle des animaux sans vertèbres[END_REF] [Turrinae] (Vanuatu, SANTO 2006 expedition, sta. DR68, 15º22.9'S, 167º13.1'E, 7-27 m, MNHN 17756), as a closely related species [START_REF] Olivera | The gastropod genus Xenuroturris (Iredale, 1929) evaluated and a new turrid Lophiotoma olangoensis described from the central Philippines[END_REF]; Turris crispa (Lamarck, 1816) COI gene sequence was manually aligned, and 28S was automatically aligned using ClustalW multiple alignment implemented in BioEdit version 7.0.5.3 [START_REF] Hall | BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT[END_REF], and the accuracy of the alignment was confirmed by eye. Genetic pairwise distances were calculated with PAUP 4.0b10 [START_REF] Swofford | On the type species of Iotyrris Medinskaya et Sysoev, 2001 (Gastropoda, Turridae)[END_REF], using the best fitting model of nucleotide substitution for each gene as defined by the program Modeltest [START_REF] Posada | Selecting models of nucleotide substitution: an application to human immunodeficiency virus 1 (HIV-1)[END_REF], in conjunction with PAUP 4.0b10, following the Akaike information criterion (AIC).

Phylogenetic reconstruction were conducted using Bayesian analysis, consisting of two Markov chains (2000000 generations each with a sampling frequency of one tree each hundred generations) run in six parallel analyses using Mr. Bayes [START_REF] Huelsenbeck | MBayes: bayesian inference of phylogeny[END_REF]. The same model of substitution used for computing the genetic distances was used for the Bayesian analysis. When the log-likelihood scores were found to stabilize, a consensus tree was calculated after omitting the first 25% trees as burn-in.

Results

Radulae and Shells

Two morphologically distinct types of radulae were found in the species initially identified as "Xenuroturris cingulifera" based on shell characters.

The first radular type is characterized by the so-called "duplex" marginal teeth, typical for the family Turridae (sensu [START_REF] Taylor | Foregut anatomy, feeding mechanisms, relationships and classification of Conoidea (Toxoglossa) (Gastropoda)[END_REF] (Fig. 1A-C). The anterior part of the tooth (closer to the tip), constituting about 0.42-0.5 of total tooth length, is solid, while the posterior part has two thickened edges, a thinner dorsal one and thicker ventral one attached to the radular membrane (Fig. 1B). The central tooth is very small, narrow, and spear shaped. The lateral teeth absent. The ratio between marginal tooth length and shell length varies from 0.47 to 0.57 % (mean 0.52, σ=0.03, n=9), that between tooth length and aperture length varies from 1.67 to 2.05 % (mean 1.90, σ=0.14, n=9).

The second radular type is characterized by "semi-enrolled" marginal teeth (Fig. 1D-F). Both edges of the marginal tooth are elevated and equally developed along the entire tooth length, and they delimit a trough between them. The anterior solid part of the tooth is absent. Central and lateral teeth are absent. The marginal teeth are proportionally slightly longer than in the duplex type: the ratio between marginal tooth length and shell length varies from 0.54 to 0.67 % (mean 0.63, σ=0.05, n=8), that between tooth length and aperture length varies from 1.90 to 2.37 % (mean 2.21, σ=0.18, n=8).

The two forms occur sympatrically, although not syntopically, in Koumac, an intensively sampled site [START_REF] Bouchet | Assessing the magnitude of species richness in tropical marine environments: exceptionally high numbers of molluscs at a New Caledonia site[END_REF] in New Caledonia; at Lifou in the Loyalty Islands; and on Espiritu Santo in Vanuatu. The shells of both forms are extremely similar and fall within the hitherto accepted [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF][START_REF] Olivera | The gastropod genus Xenuroturris (Iredale, 1929) evaluated and a new turrid Lophiotoma olangoensis described from the central Philippines[END_REF] range of intraspecific variation of "Xenuroturris cingulifera" (Figs. 23). However, after we had evidence of the two radular types, close examination of the shells revealed subtle differences.

(i) All specimens of "Xenuroturris cingulifera" have paired peripheral cords, the adapical one becoming subdivided into two by a groove with increasing shell height. In specimens with "semi-enrolled" teeth this subdivision is slightly less obvious (Fig. 3 A,D,F,H) than in specimens with "duplex" teeth. The abapical, initially single and undivided, cord also becomes subdivided at certain shell size, but only in the form with "duplex" teeth. This is shown on the specimen on Fig. 2 A, in which the abapical cord is single on the adapical whorl and becomes subdivided on subsequent whorl. Large specimens of the form with "duplex" tooth thus have a peripheral zone with four nearly even thin cords (Fig. 2 A,C); specimens with the "duplex" marginal teeth tend to have slightly less convex peripheral cords.

(ii) Another difference is the shell base and the canal. Although observations are difficult to quantify and descriptions tend to be somewhat subjective, the form with "semienrolled" teeth has slightly more attenuated siphonal canal that is than in the "duplex" form.

Both Iotyrris devoizei n. sp. and I. musivum n. sp. also have radulae with "semienrolled" teeth. In I. devoizei radular teeth are very similar to the form of "X. cingulifera" (Fig. 6 F-G) with the "semi-enrolled" teeth [= true I. cingulifera]. The central and lateral teeth were absent in one specimen, but rather well developed in another (Fig. 6 G). The marginal teeth are nearly twice as long as in I. cingulifera: the ratio between marginal tooth length and shell length varies from 0.94 to 1.15 % (mean 1.02, σ=0.09, n=5), that between tooth length and aperture length varies from 2.96 to 3.54 % (mean 3.18, σ=0.24, n=5). In Iotyrris musivum the shape of marginal teeth is also similar. The central tooth is either very small and sharp (Fig. 7 E-F) or is obtuse and fused with vestigial laterals (Fig. 7G). The marginal teeth are of intermediate length: the ratio between marginal tooth length and shell length varies from 0.75 to 0.87 % (mean 0.79, σ=0.05, n=5), that between tooth length and aperture length varies from 2.37 to 2.76 % (mean 2.58, σ=0.17, n=5).

Molecular study

For COI and 28S genes, alignments resulted in sequences of 658 and 903 bp length respectively. No indel was found for COI. Within ingroups, 97 sites were variable for COI gene, and only 14 for 28S. The Tamura-Nei model (TrN+G, with G = 0.1047) model for the COI gene and the General Time Reversible model (GTR+I, with I = 0.8579) model for the 28S gene were defined as the best fitting models.

Genetic distances are low (0.003, table 1) between specimens specimens of "Xenuroturris cingulifera" with "semi-enrolled" teeth [= true Iotyrris cingulifera], and are similar to the genetic distances found between specimens of I. devoizei, or of I. musivum (from 0 to 0.010). On the contrary, genetic distances found between specimens of "X. cingulifera" with "semi-enrolled" teeth and the specimen of "X. cingulifera" with "duplex" teeth [= X. legitima] are very high (0.551), in fact higher than the genetic distances between specimens of I. devoizei and I. musivum (0.131).

All specimens of Xenuroturris-Iotyrris clustered together for COI, but this result is not supported (Posterior Probability PP = 0.52, Fig. 4). Specimens with a "semi-enrolled" teeth are found to form a monophyletic clade (although weakly supported) that exludes the specimen with the "duplex" teeth. Within the "semi-enrolled" clade, three clades are recognized, each containing two or three specimens. Those three clades each included only specimens hypothesized to be conspecific based on shell and radula characters. Consequently, on the molecular tree, specimens of "X. cingulifera" with "semi-enrolled" teeth appear more closely related to Iotyrris devoizei and I. musivum than to the specimen of "X. cingulifera" with "duplex" teeth.

Similar results are found for 28S gene, with low genetic distances between specimens with "semi-enrolled teeth" (0.001, table 2) and higher genetic distances (0.005, table 2) between specimens of "X. cingulifera" with "semi-enrolled" teeth [true Iotyrris cingulifera] and "duplex" teeth [= X. legitima]. Monophyly of the Xenuroturris-Iotyrris clade is weakly supported (0.93). Within "semi-enrolled" clade, the three clades defined with the COI gene are found again, but only one of them is strongly supported. Relationships between those three clades and the specimen of "X. cingulifera" with "duplex" teeth [= X. legitima] are not resolved.

Discussion

Taxonomic rank of the different forms

The genetic distances between specimens of "Xenuroturris cingulifera" and the phylogenetic relationships between those specimens provide two strong arguments that confirm the hypothesis based on the observation of the radulae:

(a) with both COI and 28S gene, genetic distances between specimens displaying different radulae are very high, corresponding at least to distances found between specimens of different species, (b) with COI gene, specimens of "X. cingulifera" with "semi-enrolled" teeth are found to be more closely related to other species of Iotyrris than to the specimens of "X. cingulifera" with duplex teeth. As specific status of I. devoizei and I. musivum is not questioned, two species must be recognized within "X. cingulifera".

The species level status of the two other species, Iotyrris devoizei and I. musivum also leaves no doubt. All four species under consideration were found sympatrically in Santo, and I. devoizei and I. musivum were even found syntopically in a single underwater vacuumcleaning collecting effort. I. devoizei and I. musivum are described as new species.

Taxonomic and nomenclatural implications

Although the species considered in this paper are not unambiguously recognizable from their shells (compare, e. g., Fig. 2 F and 3 E, or 2 B and 3 C), we examined the type material of the nominal species currently subsumed in "Xenuroturris cingulifera", to ascertain which names, if any, might be applicable. Two available names are applicable to two of our species, the other two are described as new.

The type material of Xenuroturris legitima Iredale, 1929 has a short recurved siphonal canal and both peripheral cords are subdivided (Fig. 5 C,E). The name is thus applicable to the form with "duplex" radular teeth.

The syntypes of Pleurotoma cingulifera Lamarck, 1822 are badly worn specimens that render their identification difficult. The only significative character is in the peripheral cords, of which the abapical one is not subdivided, even in the largest syntype (shell length 65 mm). In our specimens of similar size with "duplex" radular teeth, that cord is always subdivided. Although some ambiguity persists, we apply the name cingulifera to the form with "semi-enrolled" marginal radular teeth. We are of the opinion that this is nomenclaturally more stable than leaving cingulifera as a nomen dubium and describing the form with "semienrolled" marginal radular teeth as a new species.

Ideally, the current name-bearing types of Pleurotoma cingulifera Lamarck, 1822 and Xenuroturris legitima Iredale, 1929 should be replaced by live-taken neotypes with known radular and molecular characteristics. This can be done only by a decision of the International Commission on Zoological Nomenclature, but we are of the opinion that this is unnecessary as long as the systematic and nomenclatural conclusions of this paper are accepted by zoologists.

The type species of Xenuroturris, by monotypy, is X. legitima [START_REF] Iredale | Queensland molluscan notes, No. 1[END_REF], and this name is thus applicable to Xenuroturris-type shells with "duplex" teeth. [START_REF] Medinskaya | The foregut anatomy of the genus Xenuroturris (Gastropoda, Conoidea, Turridae), with a description of a new genus[END_REF] proposed the monotypic new genus Iotyrris for what they had identified as Xenuroturris cerithiformis [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF] (misidentified; = Iotyrris marquesensis Sysoev, 2002), a species very similar to other species of Xenuroturris in shell characters and possessing a radula with "semi-enrolled" teeth. Although we did not include the type species of Iotyrris in our analysis, we suggest that the name Iotyrris is applicable to these turrines with Xenuroturris-type shells and "semi-enrolled" radular teeth.

Xenuroturris [START_REF] Iredale | Queensland molluscan notes, No. 1[END_REF]Iredale, 1929: 283. Type species (by monotypy): Xenuroturris legitima [START_REF] Iredale | Queensland molluscan notes, No. 1[END_REF] Xenuroturris legitima [START_REF] Iredale | Queensland molluscan notes, No. 1[END_REF]Iredale, 1929: 283, pl. 31, figs. 3-4. Selected synonymy: Xenuroturris cingulifera cingulifera -Powell, 1964 (part.) ). However, in the original description, Iredale did not fix a holotype and therefore all type specimens should be considered syntypes. Type locality: Michaelmas Cay, Queensland, Australia. Distribution: The distribution ascertained by us includes New Caledonia, the Loyalty Islands, Vanuatu, and the Philippines. The species is also recorded from South Africa (Kilburn 1983: 564-565, figs 30, 32) and Japan (Okutani 2000: 631, pl. 314, fig. 57), but this now require confirmation based on radula and/or molecular characters.

Iotyrris [START_REF] Medinskaya | The foregut anatomy of the genus Xenuroturris (Gastropoda, Conoidea, Turridae), with a description of a new genus[END_REF]Sysoev, 2001: 12. Type species: Iotyrris marquesensis Sysoev, 2002 (Fig. 8F), by fixation by Sysoev (2002) under Art. 70.3 of the Code of Nomenclature.

Iotyrris cingulifera [START_REF] Lamarck | Histoire naturelle des animaux sans vertèbres[END_REF] Pleurotoma cingulifera Lamarck, 1822: 94. Selected synonymy: Xenuroturris cingulifera cingulifera -Powell, 1964 (part.): plate 175, fig. 12, non figs. 19-20. Lophiotoma cingulifera -Olivera, 2002 (part.), fig. H3. Syntypes: 3 possible syntypes of Pleurotoma cingulifera are housed in the Muséum d'histoire naturelle de la ville de Genève (MHNG 1097/62) (Fig. 5 E-G). The largest specimen, possibly illustrated by [START_REF] Kiener | Genre Pleurotome[END_REF], has a shell length of 65 mm (MHNG 1097/62/1), which more or less matches Lamarck's indication of a size of "2 pouces 4 lignes", i.e. 63 mm. Type locality: not stated. [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF] restricted it to Mauritius, a restriction that has no standing under the ICZN. Distribution: The distribution ascertained by us includes New Caledonia, the Loyalty Islands, Vanuatu, and the Philippines. Records from Zanzibar [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF] and Guam [START_REF] Olivera | The gastropod genus Xenuroturris (Iredale, 1929) evaluated and a new turrid Lophiotoma olangoensis described from the central Philippines[END_REF] fig. H3) require confirmation based on radula and/or molecular characters.

Iotyrris devoizei n. sp.

(Fig. 6 A-G 1442, 20º46.4'S, 167º02.0'E, 47 m, 1 dd;sta. 1448, 20º45.8'S, 167º01.7'E, 20 m, sta. 1450, 20º45.8'S, 167º01.7'E, 27-31 m, 1 dd;sta. 1451, 20º47.3'S, 167º06.8'E, 10-21 m, 3 dd;sta. 1453, 20º54.6'S, 167º02.1'E, 21-30 m, 3 dd, 1 lv (Fig. 6C, 8C);sta. 1455, 20º56.8'S, 167º02.7'E, 15-20 m, 2 dd;sta. 1457, 20º46.8'S, 167º02.8'E, 5-10 m, 3 dd. DISTRIBUTION. New Caledonia, Loyalty Islands, Vanuatu, shallow water, alive in 16 to 30 m, shells from 4 to 47 m. It is possible that the species also occurs in Hawaii and the Marquesas. DESCRIPTION (holotype). Shell conical, consisting of 7 teleoconch whorls, with high spire, shell diameter to shell height 0.35, aperture height to shell height 0.33, spire height to shell height 0.49. Protoconch overgrown and eroded, light brown, of more than 3 whorls, sculptured with closely spaced axial threads. Teleoconch whorls slightly convex, spire whorls are slightly angulated on the periphery. Last whorl sharply narrowing towards attenuated, nearly straight, siphonal canal. Suture shallowly adpressed, slightly wavy. Subsutural ramp narrow, convex, with single bulging keel subdivided by two narrow and shallow grooves. The keel is strongly marked by rectangular, unevenly sized, dark red-brown spots. Immediately below the ramp are two narrow but tall, closely spaced, cords, forming the shoulder. Below them are three broadly spaced cords, equal to those on the shoulder, separated by smooth interspaces, except one narrow thread between the lower shoulder cord and upper periphery one. There are 5 more closely spaced cords on the shell base and 5 narrower and closer spaced threads on the canal. Axial sculpture absent except for inconspicuous growth lines. Aperture narowly oval. Outer lip broken, judging from the growth lines anal sinus deep, situated on the shoulder. Inner lip nearly straight, columellar part straight, callus very narrow not extending on the parietal wall. Color creamy white, with dark strong spots on the subsutural ramp, much ligher yellow narrow spots, covering all the cords of the periphery, tessellate dark closely spaced spots on the cords of the shell base, smaller and slightly ligher spots on the threads of the canal. Shell height (holotype) 17.8 mm, shell diameter 6.3 mm, last whorl height 9.0 mm, aperture height 5.9 mm. REMARKS. Paratypes are similar to the holotype in shell outline and sculpture, and appear to be juveniles. However, one of them (MNHN 17681, Fig. 6 D), with a shell length of only 11.8 mm, is already a mature male with a long penis equal in length to that of the mantle cavity. That specimen has more pronounced color spots on the shoulder and shell periphery, so that the contrast between the shell base and periphery is much less pronounced. The protoconch of the second paratype (Fig. 6 E) is best preserved, but its nucleus missing; the number of whorls is thus at least 4. The largest specimen we attribute to I. devoizei has a shell length of 27.1 mm. Iotyrris devoizei is conchologically very similar to X. kingae [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF] in terms of sculpture and colour pattern, down to the finest details. The only differences between the two is the more elongate shell of I. devoizei, with a clearly longer siphonal canal, and the slightly less bulging subsutural rim. The two species have a radula of a different type -while I. devoizei possesses semi-enrolled marginal radular teeth, X. kingae has duplex teeth (Fig. 6J). ETYMOLOGY. Musivum, Latin meaning mosaic, with reference to the colour pattern; used as a noun in opposition. OTHER MATERIAL EXAMINED. New Caledonia, Expedition Montrouzier, Koumac, sta. 1286, 20º38'-20º39'S, 164º16'-164º17'E, intertidal, 1 lv. Loyalty Islands, LIFOU 2000expedition, sta. 1421, 20º52.4'S, 167º08.5'E, 4 m, 1 lv (Fig. 7D,8D); sta. 1424, 20º54.9'S, 167º03.0'E, 4 m. DISTRIBUTION. New Caledonia, Loyalty Islands, Vanuatu, shallow water, intertidal to 16 m. DESCRIPTION (holotype). Shell conical, consisting of 5.75 teleoconch whorls, with high spire, shell diameter to shell height 0.34, aperture height to shell height 0.31, spire height to shell height 0.48. Protoconch brown, consists of 4.25 convex whorls, sculptured with closely spaced axial threads, which are slightly prosocline on most whorls, but turned to strongly opisthocline on the posteriormost part of the last protoconch whorl. There are around 25 threads on the last protoconch whorl. Teleoconch whorls nearly flat, slightly angulated at the shoulder. Last whorl sharply narrowing towards attenuated nearly straight siphonal canal. Suture shallowly impressed, slightly wavy. Subsutural ramp narrow, with single strong sharp keel, followed by narrow thread. Immediately below the ramp there are are two narrow but tall triangular in section closely spaced cords, forming the shoulder. Below there are four broadly spaced subequal cords, separated by smooth interspaces. There are 5 thinner and more closely spaced cords on the shell base and 8 narrower and closer spaced threads on the canal. Axial sculpture absent except for inconspicuous growth lines. Aperture narrowly oval.

Iotyrris musivum

Outer lip thin, evenly rounded. Anal sinus deep, situated on the shoulder. Inner lip slightly convex, columellar part straight, callus very narrow not extending on the parietal wall. Color creamy white, with regularly spaced light brown spots, covering cords of the entire shell surface and much more pronounced and more dark strong subrectangular spots on the shoulder cords. Operculum yellow, transparent, leaf-shaped, with terminal nucleus. Shell height (holotype) 12.6 mm, shell diameter 4.3 mm, last whorl height 6.6 mm, aperture height 3.9 mm. REMARKS. The holotype is a juvenile specimen. We nevertheless chose to fix it as the namebearing type, since it is clearly recognizable, because we know its radula and DNA sequence. The paratype (Fig. 7C), which is very similar to the holotype in shell outline and sculpture, has a length of 13.9 mm. The largest specimen has a shell length of 29.1 mm. In large specimens the subsutural ramp has additional thin but sharp spiral thread immediately below the suture. There are additional thin threads between the major cords on the shell periphery. Iotyrris musivum resembles Iotyrris marquesensis Sysoev, 2002 (which also has "semienrolled" marginal radular teeth) but differs in having a broader shell with relatively shorter canal. Besides, the color marks on the shoulder keels are much less pronounced in I. marquesensis and do not differ from the spots on the rest of the shell. The subsutural ramp in I. marquesensis is separated from the shoulder keels by a deep cleft, while in X. sp. only by narrow and shallow groove. From small specimens of I. cingulifera the new species differs in much larger and color spots of the shell, brighter color spots on the shoulder cords and more coarse spiral sculpture. Another species which is remotely similar to I. musivum is Lophiotoma olangoensis [START_REF] Olivera | The gastropod genus Xenuroturris (Iredale, 1929) evaluated and a new turrid Lophiotoma olangoensis described from the central Philippines[END_REF]. The new species differs in having a much more brightly colored subsutural rim and nearly straight canal, which in L. olangoensis is clearly curved to the left in apertural view. We examined the radula of a specimen from Lifou (Loyalty Islands) which we identified as L. olangoensis and it appeared to be similar to that of Xenuroturris legitima, that is consisting of duplex marginal teeth, very small and narrow central one and vestigial laterals.

Radula as a taxonomic character in "Turridae"

Since [START_REF] Mclean | A revised classification of the family Turridae, with the proposal of new subfamilies, genera, and subgenera from the Eastern Pacific[END_REF] classification of the Turridae s.l., the radula has routinely been used for subfamily and genus level allocation within Conoidea. However, relatively little correlation between foregut anatomy and shell and radular characters was found in many groups (e. g., [START_REF] Kantor Yui | Foregut anatomy and relationships of the Crassispirinae (Gastropoda, Conoidea)[END_REF][START_REF] Yui | Foregut anatomy and relationships of raphitomine gastropods (Gastropoda: Conoidea: Raphitominae). In "Systematics, Phylogeny and Biology of the Neogastropoda[END_REF]. For instance, several genera of Crassispirinae (Turridae) having very similar shells (Inquisitor Hedley, 1918, Funa Kilburn, 1988, and Ptychobela Thiele, 1925) differ significantly in radular teeth shape. In practice, similarity in shell together with dissimilarity in radula was interpreted as shell homeomorphy. For instance, [START_REF] Bouchet | Typhlosyrinx-like tropical deep-water turriform gastropods (Mollusca, Gastropoda, Conoidea)[END_REF] established the new genus Leiosyrinx (Conidae, Raphitominae), conchologically very similar to Typhlosyrinx Thiele, 1925, based on differences in their radulae. The subfamily Zonulispirinae McLean, 1971 (Turridae) was proposed mainly on the basis of its radula with "semi-enrolled" marginal teeth only, while in shell characters it is rather similar to the subfamily Crassispirinae (Turridae). However, the hypothesis that the radula better reflects relationships than the shell had never been tested by molecular data.

Kantor and [START_REF] Yui | Formation of marginal radular teeth in Conoidea (Neogastropoda) and the evolution of the hypodermic envenomation mechanism[END_REF] showed that very different marginal radular teeth in Turridae s.s. are formed in a similar way by thickening of the tooth edges, longitudinal folding and progressive elevation of the posterior edge of the tooth from the membrane in the course of tooth maturation. They illustrated this process for what they called Xenuroturris cingulifera with "duplex" teeth [= X. legitima] (Kantor and Taylor, 2000: fig. 3 g-h). Comparison of the process of maturation in both teeth types revealed that, at some point, the semi-matured teeth are rather similar in shape, and the final differences are the result of extra sclerotization of the duplex teeth that is responsible for the long anterior solid tip. The difference between "duplex" and "semi-enrolled" teeth might therefore be less profound than it seems, and its phylogenetic value was only speculative. An important result of this study is thus that species such as Iotyrris cingulifera, I. devoizei and I. musivum, with rather different shells but with similar radulae (in this case, "semi-enrolled" marginal teeth) form a clade, thus confirming that radular type is indeed reliable for revealing relationships.

The radulae of two further species with Xenuroturris-type shells were examined from animals with dried soft parts, and reveal further species pairs with "duplex" and "semienrolled" teeth. One case is Xenuroturris kingae [START_REF] Powell | The family Turridae in the Indo-Pacific. Part 1, The subfamily Turrinae[END_REF] [with "duplex" teeth] and Iotyrris devoizei [with "semi-enrolled" marginal teeth] (Fig. 6). Both are conchologically very similar in terms of sculpture and even identical in the finest details of coloration, the only significant difference being a more elongate shell, with distinctly longer siphonal canal, in X. devoizei. Such differences were earlier considered to be of intraspecific value. Thus, pending confirmation, we think that [START_REF] Olivera | The gastropod genus Xenuroturris (Iredale, 1929) evaluated and a new turrid Lophiotoma olangoensis described from the central Philippines[END_REF] Sysoev, 2002 [with "semi-enrolled" marginal teeth] (Fig. 8F) and Xenuroturris cerithiformis Powell, 1964 [with "duplex" teeth] (Fig. 8G), which differ so little in shell shape that [START_REF] Medinskaya | The foregut anatomy of the genus Xenuroturris (Gastropoda, Conoidea, Turridae), with a description of a new genus[END_REF] initially confused them.

It is remarkable that within the subfamily Turrinae a "semi-enrolled" radular tooth is found only in this clade, and it raises the question of whether they originated once in the genus -and Iotyrris is indeed monophyletic, and conchologically similar species with different radular types are the result of convergence or homoplasy -, or they appeared several times -and Iotyrris is polyphyletic and conchologically similar species with different radular types are indeed sister taxa. Regrettably, our study includes only one case where both members of the pair -X. legitima and I. cingulifera -were included in the analysis, and they ended up being not closely related in the molecular tree. Thus, although the molecular analysis confirms that differences indicated by radulae are profound, it does not rule out that similarities in shell morphologies are the result of conserved patterns rather than the result of convergence of evolved patterns.

Currently, Xenuroturris is considered a mere subgenus of Lophiotoma Casey, 1904 [START_REF] Kilburn | Turridae (Mollusca: Gastropoda) of southern Africa and Mozambique. Part 1. Subfamily Turrinae[END_REF][START_REF] Taylor | Foregut anatomy, feeding mechanisms, relationships and classification of Conoidea (Toxoglossa) (Gastropoda)[END_REF]Higo et al., 1993), the main difference being the truncated base of Xenuroturris. [START_REF] Olivera | The gastropod genus Xenuroturris (Iredale, 1929) evaluated and a new turrid Lophiotoma olangoensis described from the central Philippines[END_REF] even expressed serious doubts that Xenuroturris should be recognized as a valid subgenus, pointing out the strong similarities in shell sculpture between Lophiotoma albina [START_REF] Lamarck | Histoire naturelle des animaux sans vertèbres[END_REF] and "X. cingulifera". Our study included a single species conchologically attributable to Lophiotoma, and is not relevant on the phylogenetic relationships between the two genera.

In conclusion, and despite these reservations, our working hypothesis is that Lophiotoma, Xenuroturris and Iotyrris are all valid genera, a view that could not have been predicted from shells alone. Currently, most "turrid" genera are defined purely based on shell characters and there are anatomical or radula data for fewer than 10% of the described species. As long as molecular data exist only for a desperately small proportion of that diversity, we must be prepared that many of the currently accepted taxa are poly-or paraphyletic, at all taxonomic levels: specific, generic, and subfamilial.

  ); sta. 1304 (Expedition Montrouzier), 20°38.6'S, 164°13.2'E, 12-15 m (1 spm); LAGON, sta. 549, 22°58'S, 166°56'E, 26 m (1 spm -Fig. 3H, 8B); Atoll de Surprise, sta. 445, 18°18'S, 163°02'E, 41 m (1 spm -Fig. 3E), LOYALTY ISLANDS, LIFOU 2000, sta. 1422, 20°47.1'S, 167°07.4'E, 4 m (1 spm) (Fig. -Fig. 3B), sta. 1423, 20°54.0'S, 167°07.3'E, 12 m (2 spms -Fig. 3C-D); sta. 1425, 20°46.8'S, 167°07.2'E, 4-5 m (1 spm). VANUATU, ESPIRITU SANTO. SANTO 2006, sta. FS84, 15º33.6'S, 167º16.6'E, 5 m (2 spms sequenced, MNHN 17685and 17686) (Fig. 3I). Iotyrris devoizei n.sp. VANUATU, ESPIRITU SANTO. SANTO 2006, sta. FB72, 15º36.1'S, 166º58.5'E, 16 m (1 specimen, sequenced, MNHN 20014) (Fig. 6 A-B); sta. DS04, 15º31.5'S, 167º14.5'E, depth unknown (2 specimens, sequenced, MNHN 17681 -Fig. 6D, MNHN 17682 -Fig 6E). Iotyrris musivum n.sp. VANUATU, ESPIRITU SANTO. SANTO 2006, sta. DS04, 15º31.5'S, 167º14.1'E, 25 m (2 specimens sequenced: MNHN 17683 -Fig. 7C, MNHN 20015 -Fig.

  : plate 175, figs. 19-20, non fig. 12. Xenuroturris cingulifera -Medinskaya and Sysoev, 2002: 9, fig. 3?, fig. 6A. Lophiotoma cingulifera -Olivera, 2002, figs. 1 F, 1 G, H1, H2. Syntypes: Two type specimens of Xenuroturris legitima housed in the Australian Museum are labeled as holotype (C.57823) and paratypes (C.110457

  FB72]. ETYMOLOGY. The species is named after Patrice Petit-Devoize, biologist and diver, and a pillar of the MNHN expeditions diving team. OTHER MATERIAL EXAMINED. Vanuatu, Espiritu Santo, SANTO 2006 expedition, sta. DS04, wreck of President Coolidge, 15º31.5'S, 167º14.1'E, 25 m (2 lv, paratypes). New Caledonia, LAGON sta. 888, 20º22'S, 164º38'E, 20 m, 1 dd; Expedition Montrouzier, sta. 1269, 20º35.1'S, 165º08.1'E, 15-20 m, 1 dd; sta. 1271, 20º52.7'S, 165º19.5'E, 5-25 m, 4 dd; sta. 1311, 20º40.4'S, 164º14.9'E, 10-60 m, 1 dd; sta. 1318, 20º41.4'S, 164º14.8'E, 20-30 m, 1 dd. Loyalty Islands, LIFOU 2000 expedition, sta. 1421, 20º52.4'S, 167º08.5'E, 4 m, 2 dd; sta. 1422, 20º47.1'S, 167º07.4'E, 4 m, 2 dd; sta. 1423, 20º54.0'S, 167º07.3'E, 12 m, 1 dd; sta. 1429, 20º47.5'S, 167º07.1'E, 8-18 m, 4 dd; sta. 1435, 20º55.2'S, 167º00.7'E, 5-30 m, 2 dd; sta.

  Holotype MNHN 20015 and 1 paratype MNHN 17683. TYPE LOCALITY. Vanuatu, Espiritu Santo, wreck of President Coolidge, 15º31.5'S, 167º14.1'E, 25 m [SANTO 2006 expedition, sta. DS04].

Fig. 1 .

 1 Figure captions.

Fig. 2 .

 2 Fig. 2. Xenuroturris legitima. A -Vanuatu, SANTO 2006, sta. DR 087 (MNHN 17684), whole shell SL 57.0 mm, and close-up view of sculpture; B and C -Philippines, Panglao 2004, sta. S22, B -SL 28.4 mm, C -whole shell SL 50.5 mm, and close-up view of sculpture; D -Loyalty Islands, LIFOU 2000, sta. 1465, SL 51.5 mm; E -New Caledonia, Koumac, sta. 913, SL 39.5 mm; F -New Caledonia, Koumac, sta. 944, whole shell SL 32.5 mm, and close-up view of sculpture. All shells at the same scale, scale bars of close-ups 2 mm.

Fig. 3 .

 3 Fig. 3. Iotyrris cingulifera. A -New Caledonia, Koumac, sta.1303, whole shell SL 38.4 mm, and close-up view of sculpture; B -Loyalty Islands, LIFOU 2000, sta. 1422, SL 28.4 mm; C-D -Loyalty Islands, LIFOU 2000, sta. 1423, C -SL 22.4 mm, D -whole shell SL 23.0 mm, and close-up view of sculpture; E -New Caledonia, Surprise Atoll, sta. 445, SL 31.2 mm; F -New Caledonia, Koumac, sta. 941, whole shell SL 32.5 mm, and close-up view of sculpture; G -New Caledonia, Touho, sta. 1240, SL 41.5 mm; H -New Caledonia, sta. 549, whole shell SL 44.5 mm, and close-up view of sculpture; I -Vanuatu, Santo 2006, sta. FS 084, SL 15.6 mm. All shells at the same scale, scale bars of close-ups 2 mm.

Fig. 4 .

 4 Fig. 4. Trees obtained with COI gene (on the left) and 28S gene (on the right), using Bayesian approach. Posterior probabilities are indicated above nodes.

Fig. 6 .

 6 Fig. 6. A-G. Iotyrris devoizei n. sp. A-B -holotype, MNHN 20014 (the hole in the back results from drilling to extract the radula). C -Loyalty Islands, LIFOU 2000, sta. 1453, 21-30 m, SL 19.9 mm. D -paratype, MNHN 17681, SL 11.8 mm; E -apertural and dorsal views of paratype, MNHN 17682, SL 10.2 mm. F -radula of holotype. Gradula of the specimen in Fig. 6 C. H-J. Xenuroturris kingae Powell, 1964, New Caledonia, Koumac, 15-20 m. H -SL 17.4 mm. I -apertural and dorsal views, SL 18.0 mm. J -radula of the specimen in Fig. 6 I. All shells at the same scale. Scale bars for the radulae 50 µm.

)

  TYPE MATERIAL. Holotype MNHN 20014 and 2 paratypes MNHN 17681, 17682. TYPE LOCALITY. Vanuatu, south of Espiritu Santo, Elia Island, 15º36.1'S, 166º58.5'E, 16 m [SANTO 2006 expedition, sta.

  figs 2B1 and 2B4 represent Iotyrris devoizei, while figs 2B2-3 and 2B5 represent X. kingae. The two species co-occur in Hawaii and the Marquesas (based on Olivera's illustrations) and in New Caledonia (this paper). Another case is Iotyrris marquesensis

Table 1 .

 1 Genetic pairwise distances for COI gene. The last line for each entry in first column represents the Genbank accession number.

Acknowledgements

The present research was carried out during a visiting curatorship of YK in MNHN and the senior author wants to express his thanks to Philippe Maestrati, Virginie Héros, and especially Pierre Lozouet, for expertise and assistance during his stay in Paris. Key material for molecular studies originates from the MNHN-IRD-PNI Santo 2006 expedition, and we thank Patrice Petit de Voize, Laurent Albenga and Jacques Pelorce for collecting the specimens during daily dives during 6 weeks of sustained bad weather. Preliminary sorting of the material to morphospecies was accomplished by Alexander Sysoev and Richard Kilburn, as part of the New Caledonia "turrid factory" project. We express our thanks to Dr. Jason Biggs who shared with us unpublished information and photographs of different species of Xenuroturris, and to two anonymous reviewers for the valuable comments and suggestions. The Total Foundation supported the LIFOU 2000, PANGLAO 2004 and SANTO 2006 expeditions. The work was partially supported by a grant of the Russian Foundation for Basic Research, No. 06-04-48462.