VENUS 75 (1–4): 27–38, 2017 DOI: http://doi.org/10.18941/venus.75.1-4_27New Siphonochelus from Mozambique ©The Malacological Society of Japan27

Siphonochelus japonicus (A. Adams, 1863) and Siphonochelus nipponensis Keen & Campbell, 1964, and Their Intricate History with the Description of a New Siphonochelus Species from Mozambique (Gastropoda: Muricidae)

Roland Houart* Institut royal des Sciences naturelles de Belgique rue Vautier, 29, B-1000 Bruxelles, Belgium

Abstract: The identity of Siphonochelus japonicus A. Adams, 1863 and S. nipponensis Keen & Campbell, 1964, both described from Japan, is discussed and updated. A neotype is here designated for S. japonicus. A new Siphonochelus species S. mozambicus is described from Mozambique and compared to the Japanese species, to S. arcuatus (Hinds, 1843) and S. pentaphasios (Barnard, 1959) both from South Africa, to S. rosadoi Houart, 1999 from Mozambique and to S. stillacandidus Houart, 1985 from Madagascar.

Keywords: Muricidae, Typhinae, Siphonochelus, new species, Indo-West Pacific

Introduction

There is a great deal of confusion between Siphonochelus (Siphonochelus) japonicus (A. Adams, 1863) and S. (S.) nipponensis Keen & Campbell, 1964 due to the misidentification of the paratype of S. nipponensis. The holotype of S. nipponensis was in the Akibumi Teramachi collection at the time of description and is now at the Toba Aquarium, Japan. The paratype of S. nipponensis is deposited at Stanford University, and is actually a young specimen of a probably still undescribed species. It possesses a broad last teleoconch whorl, narrower spire whorls, more rounded anal tubes and a broad, rounded protoconch, in contrast to S. nipponensis, which has a more elongate last whorl and flattened tubes. This paratype was later illustrated by D’Attilio (1975: 53) who figured a detail of the anal tube, by Radwin & D’Attilio (1976: pl. 32, fig. 9) and by D’Attilio & Hertz (1988: 56). D’Attilio (1975) compared the anal tubes of S. syringianus (Hedley, 1903), S. japonicus and S. nipponensis, but what he then illustrated as S. japonicus is actually S. nipponensis and his figure of S. nipponensis is most probably a detail of the misidentified paratype. The image of the shell illustrated by Radwin & D’Attilio (1976: pl. 32, fig. 9) is too small to be identified with certainty, but in their chapter “Supplementary Data on Figures” the authors noted that the illustrated shell is SUPTC 9730 (= Stanford University, Paleontological Type Collection) and the identification number is the registration number of the paratype. To complicate matters, this paratype was also illustrated in D’Attilio & Hertz (1988: 56, fig. 64). It is not noted in the text that the illustrated specimen is the paratype, but D’Attilio & Hertz (1988: 37) argued that all the drawings were made possible by loans of specimens from friends,

* Corresponding author: [email protected] http://zoobank.org/urn:lsid:zoobank.org:pub:43B59357-B1E2-43E5-B47B-9213E9B098F5 28 R. Houart colleagues and institutions. Comparison of the drawing, here reproduced (Fig. 2D) with a photo of the paratype (Fig. 2C) leaves no doubt about its identity. Early in the 1980s, I examined this paratype on loan from Stanford University and also wrongly identified it as S. nipponensis together with a specimen from my collection (Fig. 4E–G). Both should be identified now as Siphonochelus sp. The misidentification of this paratype by Keen & Campbell (1964) and other authors, including myself, is understandable because the shell morphology of the species in Siphonochelus and in a few other typhine genera seems to be similar. However, even minor but notable and stable differences are useful to separate them on a specific basis. Important characters include 1) spiral ornamentation and form, number and ornamentation of the axial varices; 2) form, width and length of the siphonal canal; 3) form, placement and to a lesser degree orientation of the anal tubes; 4) form and size of the protoconch, of the last teleoconch whorl and of the subsutural ramp. All of these criteria are of importance in species-level separation within typhine genera. Another important factor leading to the misidentification of both species is the absence until now of any type material of Siphonochelus japonicus (see under that species). The genus Siphonochelus is divided into three subgenera: Siphonochelus s.s., Siphonochelus (Trubatsa) and Siphonochelus (Choreotyphis) (Houart, 2013). In WoRMS (World Register of Marine Species) both subgenera are noted as “alternate representation.” Currently there are 14 valid species of Siphonochelus s.s. described from the Indo-West Pacific: Siphonochelus (Siphonochelus) aethomorpha Houart & Héros, 2015; S. (S.) angustus Houart, 1991; S. (S.) arcuatus (Hinds, 1843); S. (S.) boucheti Houart, 1991; S. (S.) generosus Iredale, 1936; S. (S.) japonicus (A. Adams, 1863); S. (S.) nipponensis Keen & Campbell, 1964; S. (S.) pentaphasios (Barnard, 1959); S. (S.) rosadoi Houart, 1999; S. (S.) solus Vella, 1961; S. (S.) stillacandidus Houart, 1985; S. (S.) syringianus (Hedley, 1903); S. (S.) transcurrens (von Martens, 1902); S. (S.) virginiae (Houart, 1986). An additional species is described in this paper.

Material and Methods

Material: The material studied here originates from the National Science Museum, Tokyo (now National Museum of Nature and Science, Tsukuba), Japan, from the Toba Aquarium, Japan, from Stanford University, Stanford, California, USA, from the personal collection of the author, from the MAINBAZA Campaign in the Mozambique Channel and from the KAVIENG 2014 Campaign off New Ireland, Papua New Guinea. The MAINBAZA expedition in the Mozambique Channel took place in April 2009 on board R/V Vizconde de Eza, a Research Vessel from the Secretaria del Mar of the Spanish Ministerio de Medio Ambiente, Medio Rural y Marino, as part of a joint project between the Muséum national d’Histoire naturelle (MNHN; principal investigator: Philippe Bouchet) and Instituto Espanol de Oceanografia (IOE; principal investigator: Ana Ramos). Forty-six hauls were conducted at depths between 100 and 1,800 meters on four transects off Maputo, Inhambane, Bazaruto and the mouth of the Zambezi. The KAVIENG 2014 campaign took place in June 2014 (Kavieng Lagoon Biodiversity Survey) and from August 27 to September 7, 2014 (deep water). The expedition (principal investigators: Philippe Bouchet, Jeff Kinch, Claude Payri) was part of the Our Planet Reviewed expeditions organized jointly by the Muséum national d’Histoire naturelle (MNHN), Pro-Natura International (PNI) and Institut de Recherche pour le Développement (IRD), with support from Papua New Guinea’s National Fisheries Authority. The lagoon survey took place in June, based at the Nago Island Mariculture and Research Facility, and in August on board R/V Alis; the deep-water component, part of Tropical Deep-Sea Benthos, took place in September on board R/V Alis. Methods: The characters used to describe the shell morphology are the general aspect of the New Siphonochelus from Mozambique 29

Fig. 1. Method for determining diameter, height and counting the number of protoconch whorls (scale bar = 500 μm). shell, its shape and size and colour; the shape of the spire and number of protoconch and teleoconch whorls, features of the protoconch, the shape of the teleoconch whorls and features or form of the suture and of the subsutural ramp, of the axial and spiral sculpture and of the aperture and siphonal canal. When known, the characters of the operculum and radula are also used. The description is based on the holotype and the paratypes. The method for determining diameter, height and counting the number of protoconch whorls is explained in Fig. 1. The bathymetric range given here for living specimens is provided using the inner values of the recorded depths: the largest value of the minimum values and the lowest value of the maximum values of all the recorded ranges. Abbreviations: CP – chalut à perche (beam trawl); CC – chalut à crevettes (shrimp trawl) ; dd – empty shell(s); lv – live collected specimen(s); NHMUK – Natural History Museum, London, UK; MNHN – Muséum national d’Histoire naturelle, Paris, France ; NSMT – National Museum of Nature and Science, Tsukuba, Japan; RH – collection of Roland Houart; SAMC – South African Museum (Izeko), Cape Town, South Africa; SUPTC – Stanford University Paleontological Type Collection; ZMB – Museum für Naturkunde der Humboldt Universität zu Berlin, zoologisches Museum. Terminology used to describe the spiral cords (convex part of teleoconch whorl: after Merle 2001): P – primary cord; P1 – shoulder cord; P2 – second primary cord.

Systematics

Genus Siphonochelus Jousseaume, 1880 Subgenus Siphonochelus Jousseaume, 1880 Type species (by original designation): Typhis arcuatus Hinds, 1843, South Africa.

Siphonochelus (Siphonochelus) japonicus (A. Adams, 1863) (Figs 2A; 3A–G)

Typhis japonica A. Adams, 1863: 374. Typhis (Siphonochelus) japanicus (sic) ― Habe, 1961: 53, pl. 27, fig. 2. Siphonochelus (Siphonochelus) japonicus ― Keen & Campbell, 1964: figs 28, 32. 30 R. Houart

Fig. 2. A. Siphonochelus (Siphonochelus) japonicus, 7.5 mm shell length, NSMT-Mo 44065, Tosa Bay, Shikoku, Japan, 200 m deep. B. Siphonochelus (Siphonochelus) nipponensis (young specimen), 6.6 mm shell length, NSMT-Mo 44066, Sagami Bay, Honshu, Japan; C–D. Siphonochelus (Siphonochelus) sp. C, paratype of S. nipponensis, SUPTC 9730, 7 mm shell length, trawled off Tosa, Japan, 33°20´N, 133°40´E, in excess of 200 m deep; D, scan of the drawing in D’Attilio & Hertz (1988: fig. 64) (reproduced with the permission of David P. Berschauer, co-editor of The Festivus).

Siphonochelus (Lyrotyphis) japonicus ― Habe, 1968: 83, pl. 27, fig. 2. Siphonochelus japonicus ― Kuroda, Habe & Oyama, 1971: 218 (Japanese), 143 (English), pl. 169, fig. 12; Okutani & Habe, 1975: 108; D’Attilio & Hertz, 1988: 55, fig. 63, (b–d only). Siphonochelus (Siphonochelus) nipponensis ― Houart, 1991: figs 28–29, 52 [not S. nipponensis Keen & Campbell, 1964]. Siphonochelus nipponensis ― Houart, 1999: fig. 13; Tsuchiya, 2000: 381, pl. 189, fig. 81 (only); Tsuchiya, 2017: 953, 290 (pl. 246), fig. 6 [not S. nipponensis Keen & Campbell, 1964]. Not Siphonochelus japonicus ― D’Attilio, 1975: 53, text fig.; Houart, 1997: 291; Houart, 1999: fig. 14; Houart, 2008: pl. 398, figs 8a, 8b; Houart & Héros, 2008: 469, figs 6H, K [= Siphonochelus nipponensis]. Not Siphonochelus (Siphonochelus) japonicus ― Houart, 1991: figs 30, 51 [= Siphonochelus nipponensis].

Type locality: Japan, Wakayama Prefecture, Nada-cho (here designated). Type material: Neotype, 8.9 mm, Japan, Wakayama Prefecture, Nada-cho, ex RH, NHMUK 20170292. The type material of Siphonochelus japonicus could not be located in the NHMUK when I visited there in 1986. A second careful search by Andreia Salvador (curator of Marine Mollusca) was also unsuccessful. Neither is it in the Museum of Victoria in Melbourne, Australia, where some types of A. Adams are deposited (Boyd & Phillips, 1985) nor in the Redpath Museum of Canada in Montreal (Kuroda & Habe, 1954). A neotype (Fig. 3A–C) is here designated in order to define the nominal taxon objectively (ICZN Art. 75.1), the shell morphology of which is as close as possible to the original description. Original description: T. testa oblongo-ovata, sublævigata, castanea, spira elata, apice mammillato, quinquefariam varicosa, varicibus rotundis, funiculatis, interstitiis tubulis pallidis, oblique truncatis, mediocribus instructis ; apertura ovata, integra, canali brevi, clauso, subrecto. Hab. Uraga, 21 fathoms. This species is small, but very peculiar. It has rounded varices and rather short obliquely New Siphonochelus from Mozambique 31

Fig. 3. A–G. Siphonochelus (Siphonochelus) japonicus; A–C, neotype, NHMUK 20170292, 8.9 mm shell length, Nada-cho, Wakayama Prefecture, Japan; D–G, RH, 9.4 mm shell length, Cape Hino, Wakayama Prefecture, Japan, 40–50 m deep. H–K. Siphonochelus (Siphonochelus) nipponensis; H, holotype, Toba Aquarium TT 1012, 10.8 mm shell length, off Tosa, Japan, 33°20´N, 133°40´E, in excess of 200 m deep (photo courtesy by K. Hasegawa); I–K, RH, 10.9 mm shell length, East China Sea, 180 m deep. truncate tubes, which externally form pseudo-varices or rib-like ridges, extending down between the proper varices of the whorls. Description of the neotype: Shell small for genus, 8.8 mm in length and 4.6 mm in width. 32 R. Houart

Fig. 4. A–D. Siphonochelus (Siphonochelus) nipponensis; A–C, RH, 13.7 mm shell length, Aliguay Island, Philippines, 380 m deep; D, MNHN, 9.4 mm shell length, KAVIENG stn. DW4485, New Ireland, Papua New Guinea, 02°26´S, 149°54´E, 240–242 m deep. E–G. Siphonochelus (Siphonochelus) sp., RH, 9.2 mm shell length, off Kushimoto, Japan, 384–421 m deep. H–M. Siphonochelus (Siphonochelus) mozambicus n. sp.; H–J, holotype, MNHN IM-2000-33180, 5.9 mm shell length, MAINBAZA, stn. CP3132, Mozambique Channel, Maputo transect, 25°11´S, 35°02´E, 101–102 m deep; K–M, paratype, MNHN IM-2000-33181, 6.1 mm shell length, MAINBAZA stn. CP3132, Mozambique Channel, Maputo transect, 25°11´S, 35°02´E, 101–102 m deep. New Siphonochelus from Mozambique 33

Fig. 5. A–C. Siphonochelus (Siphonochelus) arcuatus, MNHN, 11.5 mm shell length, southeast of Barrow Point, Mozambique, 25°28´S, 44°25´E, 203–210 m deep. D. Siphonochelus (Siphonochelus) pentaphasios, syntype SAMC A4949, 11 mm shell length (courtesy of A. P. Marais, Edenvale, South Africa), off Cape Point, South Africa. E–G. Siphonochelus (Siphonochelus) stillacandidus, holotype, MNHN IM-2000-259, 8.4 mm shell length, Northeast of Mozambique Channel, 12°36´S, 47°38´E, 1100–1150 m deep, Banc du Leven (photo courtesy of M. Caballer, MNHN). H–I. Siphonochelus (Siphonochelus) rosadoi, MNHN, 9.7 mm shell length, MAINBAZA, Mozambique Channel, Zambeze transect, 19°35´S, 36°46´E, 518–524 m deep.

Biconical, broadly ovate, smooth. Subsutural ramp narrow, strongly sloping, weakly concave. Light tan with weakly darker spire; last whorl darker coloured at adapical part of varices and with brown band below periphery. Spire high with two protoconch whorls and four broad, convex, smooth teleoconch whorls. Suture weakly adpressed. Protoconch with smooth, rounded, glossy whorls. Width 900 µm; height 600 µm. Axial sculpture of teleoconch whorls consisting of four rounded varices from first to last whorl and low, narrow, intervariceal rib, connecting base of anal tube, with low depressed area between axial varix and rib. Spiral sculpture only consisting of P1 with rounded anal tubes and P2 (shoulder). Anal tubes partially broken. Aperture small, ovate. Columellar lip narrow, smooth; rim partially erect abapically; outer lip weakly erect, smooth within. Siphonal canal short, broad, strongly tapered abapically, ventrally sealed. Distribution: Known with certainty only from Japan, from Tosa Bay (Kochi Prefecture) to Uraga (Kanagawa Prefecture), living at 20–200 m. 34 R. Houart

Remarks: As pointed out by Keen & Campbell (1964: 51), Keen (1944) was the first to recognize Siphonochelus japonicus as a distinct species. It was considered conspecific with Siphonochelus arcuatus (Hinds, 1843) from South Africa by Sowerby (1874), followed by Tryon (1880: 239). It differs from S. arcuatus in having a smaller, more globose shell with rounded axial varices instead of sharp varices in S. arcuatus. To my knowledge, Habe (1961: pl. 27, fig. 2) was the first to illustrate the correct species, as here recognized by that name, followed by Keen & Campbell (1964: figs 28 and 32). The shell illustrated by Tsuchiya (2000: pl. 189, fig. 82 and 2017: 291 [pl. 247], fig. 1) as S. japonicus is probably another unnamed species. Siphonochelus japonicus could be confused with the paratype of S. nipponensis (see above) but S. japonicus differs from this paratype (Fig. 2C–D) and the specimen in my collection (Fig. 4E–G) in having a smaller protoconch, broader spire whorls relative to the width of the last teleoconch whorl, broader and higher axial varices, a narrower aperture, an adpressed suture as opposed to impressed in Siphonochelus sp. and a broader siphonal canal. Siphonochelus japonicus also lives at 20–200 m depth while specimens of Siphonochelus sp. live at over 200 m depth. Adams (1863: 374) mentions five varices in its original description as “quinquefariam varicosa” but actually there are four varices per whorl in the specimens I examined, although a varix from the penultimate whorl occasionally partly overlaps the last whorl (here noted as varix 5 in Fig. 3G) which could have been considered as a fifth varix by the author.

Siphonochelus (Siphonochelus) nipponensis Keen & Campbell, 1964 (Figs 2B; 3H–K; 4A–D)

Siphonochelus (Siphonochelus) nipponensis Keen & Campbell, 1964: 50, pl. 10, figs 25 and 29. Siphonochelus nipponensis ―Matsumoto, 1979: pl. 9, fig. 8 (holotype); Higo et al., 2001: 64, fig. 2264s (holotype but considered as synonym of S. japonicus): Hasegawa, 2005: 158, fig. 8B (young specimen). Siphonochelus japonicus ― D’Attilio, 1975: 53, text fig.; Houart, 1997: 291; Houart, 1999: fig. 14; Houart, 2008: pl. 398, figs 8a, 8b; Houart & Héros, 2008: 469, figs 6H, K [not Siphonochelus japonicus (A. Adams, 1863)]. Siphonochelus (Siphonochelus) japonicus ― Houart, 1991: figs 30, 51 [not Siphonochelus japonicus (A. Adams, 1863)]. Not Siphonochelus (Siphonochelus) nipponensis ― Houart, 1991: figs 28–29, 52 [= Siphonochelus japonicus (A. Adams, 1863)]. Not Siphonochelus nipponensis ― Houart, 1999: fig. 13; Tsuchiya, 2000: 381, pl. 189, fig. 81 (only); Tsuchiya, 2017: 953, 290 (pl. 246), fig. 6 [= Siphonochelus japonicus (A. Adams, 1863)].

Type locality: Trawled off Tosa, Japan, in excess of 200 m, 33°20´N, 133°40´E. Type material: Holotype, Toba Aquarium TT no. 1012 (ex A. Teramachi collection); 1 paratype, STUPC 9730. Distribution: Siphonochelus nipponensis is known with certainty from Japan (type locality and Hasegawa, 2005), the East China Sea (RH), the Philippines (Houart, 2008), Indonesia (Kai and Tanimbar Islands) (Houart, 1997), Kavieng, New Ireland (KAVIENG, stn DW4485, new locality), Fiji and Tonga (Houart & Héros, 2008), living at 200–417 m. Remarks: Siphonochelus nipponensis was confused with S. japonicus by D’Attilio (1975) and subsequently by D’Attilio & Hertz (1988), Houart (1999, 2008) and Houart & Héros (2008). The drawings or photos illustrating S. japonicus in these publications are S. nipponensis. Siphonochelus nipponensis has a more elongate shell with much flatter anal tubes, compared to the more globose shell of S. japonicus with rounded or less flat anal tubes that are tapered at the end. Compare the New Siphonochelus from Mozambique 35 holotype of S. nipponensis (Fig. 3H) with a specimen from the Philippines (Fig. 4A–C) and from the China Sea (Fig. 4I–K) with S. japonicus (Figs 2A; 3A–G).

Siphonochelus (Siphonochelus) mozambicus n. sp. (Fig. 4H–M)

Type locality: Mozambique Channel, Maputo transect, 25°11´S, 35°02´E, 101–102 m. Type material: Holotype MNHN IM-2000-33180; 7 paratypes MNHN IM-2000-33181, 2 paratypes RH, 2 paratypes Jose Rosado (Maputo, Mozambique), 1 paratype Sandro Gori (Livorno, Italy). Material examined: MAINBAZA, stn CP3132, Mozambique Channel, Maputo transect, 25°11´S, 35°02´E, 101–102 m, 2 lv, 20 dd (holotype MNHN, 7 paratypes MNHN, 1 paratype RH); stn CP3133, Maputo transect, 25°11´S, 35°10´E, 200–201 m, 1 lv; stn CP3144, Inhambane transect, 23°33´S, 35°41´E, 171–180 m, 1 dd; stn CC3175, Maputo transect, 25°34´S, 34°11´E, 155–165 m, 1 dd. Mozambique, Ponta Techobanine, 125–140 m, 1 dd, RH; Inhaca, 125–140 m, 1 lv, RH; south Mozambique, NE Inhaca Island, 160–170 m, 2 lv (paratypes J. Rosado), 1 lv (paratype RH), south Mozambique, NE Inhaca Island, 125–145 m (1 paratype S. Gori). Distribution: Off Mozambique, living at 102–200 m. Description: Shell small for genus, up to 6.1 mm in length (holotype). Length/width ratio 2.0. Broadly lanceolate, stout, smooth. Subsutural ramp very narrow, almost horizontal or very weakly sloping, weakly concave. Spire whorls and protoconch light tan, lighter coloured on penultimate and last whorl with whitish axial varices. Empty collected shells entirely off white or dirty white. Aperture white within. Spire high with 1.5–1.75 protoconch whorls and teleoconch of up to four broad, weakly convex, strongly shouldered whorls. Suture impressed. Protoconch moderately large, broad, whorls rounded, smooth, glossy. Width 700–800 µm, height 650–700 µm. Terminal lip delicate, thin, almost straight or opisthocline. Axial sculpture of teleoconch whorls consisting of four high, strong, narrow, rounded varices from first to last teleoconch whorl, extending to tip of siphonal canal. Other axial sculpture of single, low, weakly swollen, intervariceal ridge, nearest to preceding varix. Spiral sculpture of P1 with anal tube connected to axial varix, P2 (shoulder cord), and microscopic lirae extending on anal tubes, only visible on two fresh specimens (holotype and paratype MNHN). Anal tubes flattened at base, weakly tapered and rounded at extremity, forming an angle of approximately 70° with axis of shell. Only apertural tube open and functional, other tubes closed. Aperture small, roundly ovate, forming continuous peristome. Columellar lip narrow, smooth, rim erect. Outer lip smooth within. Siphonal canal short, 19–21% of total shell length, broad at base, strongly tapered abapically, straight or very weakly dorsally bent and ventrally sealed. Operculum light brown, roundly ovate with apical nucleus. Radula unknown. Remarks: A few years ago, I first identified this small species as Siphonochelus japonicus (unpublished) although usually living deeper and at a considerable distance from the type locality, but with new material on hand, obtained during the MAINBAZA campaign, and with a better knowledge of the subfamily Typhinae, I was able to compare both populations more carefully. Siphonochelus japonicus is clearly larger, more globose and less stout, though with the same number of teleoconch whorls; the shoulder ramp is broader and shallower and the suture is adpressed rather than impressed as in S. mozambicus n. sp. Siphonochelus nipponensis is also comparatively much larger, with more flattened anal tubes, an adpressed suture rather than an impressed one as in S. mozambicus n. sp. and with a broader 36 R. Houart and less deep subsutural ramp. The six other Siphonochelus species occurring in the western Indian Ocean, i.e. Madagascar, Mozambique and southern Africa are: S. (S.) aethomorpha Houart & Héros, 2015, S. (S.) arcuatus (Hinds, 1843), S. (S.) pentaphasios (Barnard, 1959), S. (S.) rosadoi Houart, 1999, S. (S.) stillacandidus Houart, 1985 and S. (S.) transcurrens (Martens, 1903). They all differ markedly from the present new species, as do the other Indo-West Pacific species. Siphonochelus (S.) arcuatus (Fig. 5A–C) is comparatively much larger with the same number of teleoconch whorls, has broader teleoconch whorls with sharper axial varices, an adpressed suture as opposed to an impressed one in the new species and a protoconch almost three times larger. Siphonochelus (S.) pentaphasios (Fig. 5D) differs in the same characters as above, but also in being broader and in having teleoconch whorls with five varices per whorl instead of four. Siphonochelus (S.) stillacandidus (Fig. 5E–G) differs in having a more elongate shell, more strongly shouldered teleoconch whorls, a more acute higher spire, a narrower siphonal canal and narrower, more rounded anal tubes. Siphonochelus (S.) rosadoi (Fig. 5H–I) also differs in having a larger, broader shell with a more acute spire, a more circular aperture, a comparatively narrower siphonal canal and an adpressed suture rather than an impressed one as in S. (S.) mozambicus n. sp. The two other Indian Ocean species, S. transcurrens and S. aethomorpha differ in many ways and do not need to be compared here.

Acknowledgements

I am grateful to Philippe Bouchet (MNHN) for giving me the opportunity to study the material collected during the MAINBAZA and the KAVIENG campaigns and for additional information about the expeditions. I thank also Kazunori Hasegawa (NSMT) for the scan of a colour photo of the holotype of Siphonochelus (S.) nipponensis; Akihiko Matsukuma (then in NSMT) for the loan of specimens of S. (S.) japonicus and S. (S.) nipponensis in 1987; Andreia Salvador (Natural History Museum, United Kingdom), for her help in searching the type material of S. (S.) japonicus; Marien Faber, Duivendrecht, The Netherlands for useful bibliographic information and scan of a publication; David P. Berschauer, co-editor of The Festivus for the permission to reproduce a drawing and John Wolff (Lancaster, Pennsylvania, USA), for checking the English text and for other comments. Manuel Caballer (MNHN) provided the images of the MNHN holotype of S. (S.) stillacandidus, E-Recolnat Project: ANR-11-INBS-0004. I am also grateful for the loan of the paratype of S. (S.) nipponensis from the Stanford Museum early in the eighties (written correspondence mislaid).

References

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(Received June 3, 2017 / Accepted September 13, 2017) 38 R. Houart

エントツヨウラクとニッポンエントツヨウラクの分類学的混乱の歴史， およびモザンビーク産のエントツヨウラク属の 1 新種の記載 （腹足綱：アッキガイ科）

Roland Houart

要 約

エントツヨウラク属 Siphonochelus Jousseaume, 1880 の日本産の 2 種，エントツヨウラク S. japonicus A. Adams, 1863 とニッポンエントツヨウラク S. nipponensis Keen & Campbell, 1964 の同定には著しい混乱が あった。これは S. nipponensis のパラタイプの誤同定に寄るところが大きい。本タクソンのホロタイプは 寺町コレクションに（現在は鳥羽水族館所蔵），パラタイプはスタンフォード大学の地学コレクションに 保管されているが，後者の方がのちの多くの論文に図示されている。このたび，鳥羽水族館所蔵の S. nipponensis のホロタイプの写真を基に再検討を行った結果，パラタイプは未記載と考えられる別種の未成 熟個体であることがわかった。一方の S. japonicus の方もホロタイプが失われていることで，混乱してい る状況があったため，ネオタイプを指定することで同定を確定させた。さらに，モザンビークからエント ツヨウラクに近似した 1 新種を記載し，日本産の 2 種を含む既知種と比較を行った。

Siphonochelus japonicus A. Adams, 1863 エントツヨウラク 本種は南アフリカの S. arcuatus（Hinds, 1843）の異名とされることが多かったが，より小型で膨らみが 強く，縦張肋は尖らず丸みが強いことで区別される。波部（1961：続原色日本貝類図鑑）は初めて本種を 正しく図示している。土屋（2017：日本近海産貝類図鑑第二版）がこの名前で図示しているのは，未記載 の別種と思われる。

Siphonochelus nipponensis Keen & Campbell, 1964 ニッポンエントツヨウラク 従来しばしばエントツヨウラクと混同されており，例えば土屋（2017：日本近海産貝類図鑑第二版）が 本種として図示しているのは，エントツヨウラクである。エントツヨウラクと比較して，貝殻はより細長 く伸び，後水管がやや平たく伸長する。

Siphonochelus mozambicus n. sp.（新種） 殻は本属としては小型，殻長／殻径比 2.0，やや幅広い槍の穂先形。縫合下の段差は非常に狭く，弱く 凹状となる。原殻はやや大きく 1.5～1.75 層，平滑で幅広い。成殻は最大 4 層。各螺層に 4 本の断面が丸 い縦張肋がある。後水管は基部がやや平たく，開口部は丸く細まり，殻軸に対して 70° の角度となる。殻 口は小さく卵形で連続する。前水管は短く，殻長の 19～21％，基部は太く，先端に向かって急激に細ま り，直線的あるいは弱く背部へ曲がる。 タイプ標本：ホロタイプ MNHN IM-2000-33180，殻長 6.1 mm。 タイプ産地：モザンビーク海峡，25°11´S, 35°02´E，水深 101～102 m。 著者は当初本種をエントツヨウラクに同定していたが，のちに追加標本を調査することにより，種レベ ルで区別されることが分かった。エントツヨウラクは本種よりも明らかに大型で膨らみが強く，縫合下の 括れが浅い。