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Symmetromphalus mcleani Beck, sp. nov. Figs 15–17 [ZooBank LSID: urn:lsid:zoobank.org:act: D1AFECE2-136D-4CFD-A32C-47B5B300DC17] Type material. Holotype (female) [MNHN-IM-2000-38690] from STARMER II PL20 and two paratypes (male and juvenile) from STARMER II PL20 [Paratype 1, male: MNHN-IM-2000-38691; Paratype 2, juvenile: MNHN-IM- 2000-38692] as well as two paratypes from [STARMER II, PL16] in NSMT [Paratype 3, female, NSMT-Mo 79425; Paratype 4, male, NSMT-Mo 79426], and two paratypes [from STARMER II, PL16] in SMF [Paratype 5, empty shell, SMF 370385; Paratype 6, empty shell, SMF 370386]. Type locality. North Fiji Basin, (White Lady) active hot vents, 16° 59.50′ S – 173° 55. 47′ W. Material examined. The type material and from Lau Basin: BIOLAU, BL03, 1 male and 6 juvenile specimens [SMF 370387]; BIOLAU, BL12, 4 males and 2 juvenile specimens [NSMT-Mo 79427]. From North Fiji Basin: STARMER II, PL16, 17 females, 2 males, and 19 juvenile specimens [SMF 370388]; STARMER II, PL18, 1 female and 12 juvenile specimens [NSMT-Mo 79428]; STARMER II, PL19, 8 empty shells and 1 juvenile specimen [MNHN-IM-2020-12945]; STARMER II, PL20, 13 females, 5 males, and 2 empty shells [SMF 370389]. Distribution. North Fiji Basin and Lau Basin at bathyal hydrothermal vents. Etymology. Species is named after James H. McLean, Los Angeles County Museum of Natural History. Description. Shell (Figs 15, 16A–B). Small for genus, almost limpet-shaped with remnants of shell-coiling at apex, even in adults, aperture irregularly oval in outline reflecting up to 12 radial broad ribs which appear not before 4-5 mm shell length; protoconch diameter 180 μm; juvenile teleoconch smooth, at shell length exceeding 1.0 mm with fine radial riblets (in adults more than 200 riblets present), which can only be seen by SEM, riblets finely knobbed; periostracum white to yellowish-brown, slightly overhanging and flexible at shell margin, in adults additionally slightly scaly at shell margin; apex approximately at mid-line, its position changes during shell growth from posterior shell margin to center of the shell; shell margin not in level but describing an irregular line corresponding to the surface of the substratum; interior of shell white, of silky brightness; horseshoe-shaped scars of shell muscles weakly marked; inner surface (except muscles scars) with numerous irregular micropores into which the filamentous papillae of the pallial surface fit, pores penetrate the ostracum but not the periostracum. Dimensions. Largest specimen (empty shell) length 8.9 mm, width 5.1 mm, height 2.5 mm; holotype female 7.1 mm x 4.2 mm x 2.0 mm, paratype 1 (male) 5.9 mm x 3.8 mm x 2.0 mm. Radula (Figs 16D–F). Rhipidoglossate, as is typical for genus, formula 10–12 x 4 x 1 x 4 x 10–12; rachidian and four lateral teeth of similar shape, rachidian cusp slightly larger than cusp of first lateral, cusps of laterals increasing in size distally, no serrations except at distal margin of cusp of fourth lateral; there, the lowermost serration is most prominent; only 10–12 marginal pairs of teeth present, bearing finely denticulated cusps with distal, tongue-like processes. Soft parts (Figs 15A, D, H, 16C, E, 17A–E). Head with short tentacles directed posteriorly; in males, the left cephalic tentacle is transformed and enlarged to function as a penis, snout transformed, having no oral disc with marginal papillae but a large transverse furrow; neck elongated, in males with deeply marked seminal groove leading to the left cephalic tentacle; neck dorso-ventrally compressed with laterally thickened edges; eyes lacking; penis with longitudinal furrows and with a tubule at the tip. Footsole round in outline, anterior third broader than the rest, with minute slit-shaped opening of anterior foot gland; foot sides laterally and posteriorly with epipodial ridge bearing up to ten pairs of tentaculiform appendages, posterior appendages of approximately the same size as the cephalic tentacles; pallial margin smooth but pallial epithelium with numerous minute, filamentous papillae fitting into the shell micropores; pallial cavity deep containing the very large bipectinate gill which apparently is used for filter feeding, afferent membrane completely absent, massive efferent axis arises at posterior of pallial cavity on left side and reaches up to or beyond anterior margin of head, gill lamellae thin and elongate (curled in contracted condition) increasing in length from posterior to anterior; visceral mass comparatively small, gonad appears to be its essential part, rectum leads to the anus at anterior right comer of pallial cavity; shell muscle horseshoe-shaped with longish left arm and slightly shorter and broader right arm, both arms posteriorly connected by an extremely thin muscular ligament. Operculum present in all specimens examined, very thin and translucent, last [re]volutions enlarged rapidly. Remarks. S. mcleani sp. nov. is the third species of the genus Symmetromphalus which lives at active hot vents in the western Pacific. The type species, S. regularis from Mariana vents, is reported to live in dense aggregations on basalt boulders in the path of hydrothermal effluents (McLean 1990). The same is true for S. hageni reported from the surface of active smokers at Manus vents (Beck 1992a). All morphological evidence [from gill and head-foot] of the new species described here point out that S. mcleani sp. nov. is also sessile and lives as a filter-feeder. The new species’ morphology is clearly distinguished from the known species by the following characters: shell with up to 12 broad radial ribs and a slightly scaly periostracum at shell margin; shell dimensions smaller; number of marginal teeth reduced to 10–12 pairs. All specimens have intact shells with no mineral encrustations or damaged periostraca as is usual for other hot-vent taxa (e.g. species described earlier in this paper). However, as a consequence of a sessile mode of life, soft parts are in some places colonized by bacteria. At the epipodium threads of organisms similar to Beggiatoa are common. At seminal groove, coccal organisms were found to exist in dense colonies., Published as part of Chen, Chong & Sigwart, Julia D., 2023, The lost vent gastropod species of Lothar A. Beck, pp. 401-436 in Zootaxa 5270 (3) on pages 422-426, DOI: 10.11646/zootaxa.5270.3.2, http://zenodo.org/record/7860042, {"references":["McLean, J. H. (1990) A new genus and species of neomphalid limpet from the Mariana vents with a review of current understanding of relationships among Neomphalacea and Peltospiracea. The Nautilus, 104, 77 - 86.","Beck, L. (1992 a) Symmetromphalus hageni sp. n., a new neomphalid gastropod (Prosobranchia: Neomphalidae) from hydrothermal vents at the Manus Back-Arc Basin (Bismark Sea, Papua New Guinea). Annalen des Naturhistorischen Museums in Wien, 93, 243 - 257."]}

Symmetriapelta Beck, gen. nov. Figs 18, 19 [ZooBank LSID: urn:lsid:zoobank.org:act: 97289DCB-A600-4E88-8713-0984E32FFDFA] Type species. Symmetriapelta wareni sp. nov. Diagnosis. Rhipidoglossate ["]archaeogastropods["] with limpet-shaped shell of small size. Apex slightly left of mid-line, nearly at center of shell in adults, in juveniles near posterior margin of shell; in juveniles with the first teleoconch whorl present; in adults it is eroded at apex; sculpture of beaded radial ribs of varying thickness and number; aperture oval with lateral parts running almost parallel in adults; periostracum not overhanging; shell interior opaque to white with fine, coalescing, concentric lines corresponding to the shell structure, no nacre; muscle scars barely marked; depth of shell interior with minute remainder of teleoconch whorl even in adults with eroded apex. Radula with formula about 18 x 4 x 1 x about 18; of peltospirid type, first and second lateral tooth bases each with additional ridge (or node), cups of fourth lateral with delicate denticulation on inner side whereas outer side has four conspicuous denticles. Animals with eyeless head, snout with greatly thickened circumoral roll which is divided ventrally, cephalic tentacles of equal size, very thick, directed anteriorly, extending beyond margin of snout; neck short, passing over to a deep and large concave depression in which the visceral mass is embedded; depression translucent as foot sole is very thin; foot sole oval, with continuous marginal flap that is broadened and elongated anteriorly and that bears a moderate-sized slit of the anterior foot gland; epipodium well developed, it consists of a continuous basal ridge which bears about 25 anterio-lateral epipodial tentacles and two slightly solitary posterior tentacles. Pallial cavity is of moderate depth reaching to the left on half of animal length; deeper and larger on left side where it contains the gill with long afferent membrane at ventral-right side; efferent membrane fused to the pallial skirt on 80% of gill length, free tip tapering; dorsal gill lamellae short but ventral lamellae large and triangular. Anterior right part of pallial cavity short, containing anus and openings of kidney and gonad. Pallial margin adhering to the shell throughout its length, pallial skirt with micropapillae that fit into the shell pores. Visceral mass small, not filling the concave depression on dorsal side of the foot. Gonad is mostly covered by the digestive gland. Operculum absent. Etymology. Genus name has Latin roots, symmetria for symmetrical and pelta for shield. Remarks. Symmetriapelta is the first limpet-shaped peltospirid from the western and southwestern Pacific. However, the main area of [neomphaloidean] distribution is at EPR, where 11 genera are recognized (with coiled shell: Depressigyra, Lirapex, Melanodrymia, Pachydermia, Planorbidella; with limpet-shaped shell: Peltospira, Rhynchopelta, Hirtopelta, Ctenopelta, Nodopelta, Echinopelta) (Warén & Bouchet 1993). Symmetriapelta gen. nov. differs from all these genera in having an almost central apex, however, there are some characters which point to a close relationship with Nodopelta and foremost, with Echinopelta: aperture of shell with lateral margins running parallel, anatomy of the epipodium, and the presence of ridges or nodes at the bases of lateral radular teeth. While Symmetriapelta gen. nov. is different from Nodopelta in having no vestige of an operculum and no glandular pallial margin, the new taxon substantially differs from Echinopelta in the following characters: apex of shell is almost positioned centrally (as opposed to being near the shell margin), shell margin smooth, following the line of the radial ribs on the shell surface (compared with an undulating shell margin), number of epipodial tentacles about 50 (in contrast to of more than 100), periostracum with beaded radial ribs of different size (instead of hollow spines)., Published as part of Chen, Chong & Sigwart, Julia D., 2023, The lost vent gastropod species of Lothar A. Beck, pp. 401-436 in Zootaxa 5270 (3) on pages 426-428, DOI: 10.11646/zootaxa.5270.3.2, http://zenodo.org/record/7860042, {"references":["Waren, A. & Bouchet, P. (1993) New records, species, genera, and a new family of gastropods from hydrothermal vents and hydrocarbon seeps. Zoologica Scripta, 22, 1 - 90. https: // doi. org / 10.1111 / j. 1463 - 6409.1993. tb 00342. x"]}

Symmetriapelta wareni Beck, sp. nov. Figs 18, 19 [ZooBank LSID: urn:lsid:zoobank.org:act: 9D3FF7B3-B4E6-48B4-B3AA-5DB26555EC88] Type material. Holotype [MNHN-IM-2000-38693], two paratypes in MNHN [Paratype 1: MNHN-IM-2000- 38694; Paratype 2: MNHN-IM-2000-38695], two paratypes in NSMT [Paratype 3: NSMT-Mo 79429; Paratype 4: NSMT-Mo 79430], two paratypes in SMF [Paratype 5: SMF 370390; Paratype 6: SMF 370391]. Type locality. North Fiji Basin (White Lady). Material examined. The type material and BIOLAU, BL03,> 10 specimens [MNHN-IM-2020-12946]; BIOLAU, BL04,> 10 specimens and 3 empty shells [SMF 370392]; BIOLAU, BL08, 9 specimens [NSMT-Mo 79431]; BIOLAU, BL09, 1 specimen [SMF 370393]; BIOLAU, BL12,> 10 specimens [NSMT-Mo 79432]; STARMER II, PL10, 4 specimen [SMF 370394]; STARMER II, PL11, 7 specimens [MNHN-IM-2020-12947]; STARMER II, PL12,> 10 specimens [NSMT-Mo 79433]; STARMER II, PL13, 5 specimens [SMF 370395]; STARMER II, PL14, 2 specimens [SMF 370396]; STARMER II, PL15, 1 empty shell [SMF 370397]; STARMER II, PL20, 4 specimens [SMF 370398]; No data, 4 specimens [SMF 370399]. Distribution. North Fiji Basin and Lau Basin at hot-vent fields. Etymology. Species is named after Anders Warén, Swedish Museum of Natural History, Stockholm. Description. The characters defining the genus also serve as the description of the species. In addition, the following characters are worth mentioning: Shell (Figs. 18, 19B). Shell surface with three to five beaded, fine, radial riblets alternating with thicker, beaded radial ribs; these thicker ribs are extremely variable as comparison of Fig. 18A with Fig. 18E shows. There are both character states present at North Fiji and Lau vents with all possible states of transition. Dimensions. Largest specimen length 5.7 mm, width 4.1 mm, height 1.8mm; Holotype 3.9 mm x 2.6mm x 1.5 mm., Published as part of Chen, Chong & Sigwart, Julia D., 2023, The lost vent gastropod species of Lothar A. Beck, pp. 401-436 in Zootaxa 5270 (3) on page 429, DOI: 10.11646/zootaxa.5270.3.2, http://zenodo.org/record/7860042

Order NEOMPHALIDA McLean, 1990 Superfamily NEOMPHALOIDEA McLean, 1981 Family PELTOSPIRIDAE McLean, 1989 Lirapex Warén and Bouchet, 1989 Type species Lirapex humatus Warén and Bouchet, 1989 (by original designation). Diagnosis Small- to medium-sized (, Published as part of Chen, Chong, Han, Yuru, Copley, Jonathan T. & Zhou, Yadong, 2021, A new peltospirid snail (Gastropoda: Neomphalida) adds to the unique biodiversity of Longqi vent field, Southwest Indian Ridge, pp. 851-866 in Journal of Natural History 55 (13 - 14) on pages 855-856, DOI: 10.1080/00222933.2021.1923851, http://zenodo.org/record/5464198, {"references":["McLean JH. 1989. New archaeogastropod limpets from hydrothermal vents: new family Peltospiridae, new superfamily Peltospiracea. Zool Scr. 18 (1): 49 - 66. doi: 10.1111 / j. 1463 - 6409.1989. tb 00123. x.","Waren A, Bouchet P. 1989. New gastropods from East Pacific hydrothermal vents. Zool Scr. 18 (1): 67 - 102. doi: 10.1111 / j. 1463 - 6409.1989. tb 00124. x.","Waren A, Bouchet P. 2001. Gastropoda and Monoplacophora from hydrothermal vents and seeps; new taxa and records. Veliger. 44: 116 - 231. doi: 10.1111 / j. 1463 - 6409.1993. tb 00342. x.","Chen C, Zhou Y, Wang C, Copley JT. 2017 a. Two new hot-vent peltospirid snails (Gastropoda: Neomphalina) from Longqi hydrothermal field, Southwest Indian Ridge. Front Mar Sci. 4. doi: 10.3389 / fmars. 2017.00392."]}

The biodiversity of deep-sea hydrothermal vents in the Indian Ocean remains poorly characterised compared with that of their Pacific and Atlantic counterparts. Although the Longqi hydrothermal vent field is the most extensively explored vent site on the ultra-slow-spreading Southwest Indian Ridge, it is still a source of new discoveries. Here, we report and formally describe a new peltospirid snail from Longqi–Lirapex felix sp. nov. Known from only two specimens, it differs from other named Lirapex species by a depressed spire and the lack of coil loosening on the body whorl. Examinations of the external anatomy and radular characteristics agree with its placement in Lirapex, which is also supported by a molecular phylogeny reconstructed using the barcoding fragment of the mitochondrial cytochrome c oxidase I (COI) gene. This is the fifth peltospirid snail known to inhabit the Longqi field, three of which (including Lirapex felix sp. nov.) have been found nowhere else. There is growing evidence that the Longqi field represents a biogeographically unique site among Indian Ocean vents. The discovery of Lirapex felix sp. nov. adds to the unique biodiversity of Longqi field, with implications for conservation in the light of potential deep-sea mining. This work is registered in ZooBank under: urn:lsid:zoobank.org:pub:3B892762-2110-4A1E-A80D-1779CBEC5EB3.

Genus Leptogyra Bush, 1897 (Leptogyra Bush, 1897: 135���136) Type species. Leptogyra verrilli Bush, 1897, Published as part of Krol, Ekaterina N. & Nekhaev, Ivan O., 2020, Redescription of Leptogyra bujnitzkii (Gorbunov, 1946) comb. nov., the first representative of the gastropod subclass Neomphaliones from the high Arctic, pp. 446-450 in Zootaxa 4759 (3) on page 446, DOI: 10.11646/zootaxa.4759.3.13, http://zenodo.org/record/3741156, {"references":["Bush, K. J. (1897) Revision of the marine gastropods referred to Cyclostrema, Adeorbis, Vitrinella and realted genera with dexriptions of some new genera and species belonging to the Atlantic fauna of America. Transactions of the Connecticut Academy of Arts and Sciences, 10, 97 - 144."]}

Leptogyra bujnitzkii (Gorbunov, 1946) (Figure 1) Ganesa bujnitzkii Gorbunov, 1946b: p. 309, pl. 1, fig. 1a���b, v. Skenea bujnitzkii: Kantor & Sysoev 2006: p. 40, pl. 18D. Type material. 2 syntypes, R / V Sadko, det. Gorbunov, 24.07.1938, sta. 101, trawl, Zoological Institute of Russian Academy of Sciences No 1908/1. Type locality. Arctic Ocean, slope of Lomonosov Ridge, 81��50���N, 136��14���E, 3,700���3,800 m. Diagnosis. Leptogyra Bush, 1897 with skeneiform shell, thin sigmoidal growth lines, wide spiral wrinkles, wide, deep umbilicus. Central tooth of radula wide, rectangular, first three lateral teeth similar, fourth lateral tooth rather large, numerous filamentous marginal teeth. Description. Shell small (maximal shell width 3.15 mm), skeneiform, light brownish with convex rounded whorls, suture deep, periphery of penultimate whorl rounded, convex. Teleoconch surface with thin numerous sigmoidal growth lines, spiral sculpture consists of wide wrinkles (Fig. 1A, E). Almost whole surface of embryonic shell covered with irregular network sculpture, only narrow part near protoconch border smooth (Fig. 1 C���D). Aperture rhomboid with rounded angles. Umbilicus wide, deep. Periostracum, operculum and soft body unknown. According to original description operculum consist of four whorls in larger specimen, of three whorls in smaller specimen (Gorbunov 1946b). Radula (Fig. 1 F���G). n -4-1-4- n. Central tooth poorly visible on preparation, wide, rectangular, with thin cutting edge without distinct cusps. Three inner lateral teeth uniform, narrow, with small triangular cutting edge, outer lateral large, with single relatively small triangular cutting edge. Marginal teeth numerous, thin, filamentous. Measurements of syntype 1: shell height 2.45 mm, body whorl height 2.20 mm, aperture height 1.45 mm, shell width 3.15 mm, aperture width 1.65 mm, diameter of protoconch 308 ��m, diameter of the initial part of protoconch 67 ��m, number of whorls 3.4, number of protoconch whorls 0.7. Measurements of syntype 2: shell height 2.30 mm, body whorl height 2.05 mm, aperture height 1.35 mm, shell width 2.95 mm, aperture width 1.50 mm, diameter of protoconch 300 ��m, diameter of the initial part of protoconch 67 ��m, number of whorls 3.5, number of protoconch whorls 0.7. Distribution. Known only from the type locality. Remarks. We suggest that Ganesa bujnitzkii Gorbunov, 1946 actually belongs to the genus Leptogyra. The representatives of this genus have the same pattern of protoconch sculpture, consisting of an irregular network vanishing towards adult whorls (Marshall 1988). The teleoconch sculpture of Leptogyra bujnitzkii resembles that of Leptogyra by the presence of prosocline sigmoidal growth lines and spirally arranged wrinkles or riblets (Bouchet & War��n 1993; Marshall 1988; War��n & Bouchet 2009). The radular morphology of Leptogyra bujnitzkii is the same as in the majority of Leptogyra species (see Marshall 1988). The irregular network sculpture on the protoconch and the sigmoidal growth lines are also present in Xyleptogyra Marshall, 1988 and Leptogyropsis Marshall, 1988. However, both genera differ from Leptogyra bujnitzkii in radular morphology (Marshall 1988). Leptogyropsis has three curved lateral teeth and a deeply medially split central tooth that is curved laterally. Xyleptogyra has three strongly curved lateral teeth and a wide laterally curved central tooth (Marshall 1988). Marshall (1988) recognized that Leptogyra constricta Marshall, 1988 and Leptogyra patula Marshall, 1988 have only three lateral teeth. However, he mistakenly interpreted the fourth rather large lateral tooth as innermost marginal. Leptogyra inflata War��n & Bouchet, 1993 has five lateral teeth according to War��n & Bouchet (1993), however, only four laterals can be recognized on the figures provided by these authors. In accordance with Hess et al. (2008), we consider the presence of four lateral teeth as a diagnostic feature of Leptogyra. Leptogyra bujnitzkii was described in a book presenting results of Soviet studies in the Siberian seas and the Arctic Ocean during the 1930s. The name Ganesa bujnitzkii (like other newly-introduced species names) was first mentioned in the first chapter of this book summarizing ecological, distributional, and biogeographical data for all sea floor fauna known for this region (Gorbunov 1946a). This publication also contains information about the collection site for G. bujnitzkii. However, the morphological description is given in another chapter (Gorbunov 1946b), which constitutes the valid description of this taxon according to the article 13.1 of the International Code of the Zoological Nomenclature. The coordinates of the type locality given by Gorbunov (1946a) (82��51��� N, 137��23��� E) (Fig. 2B, red star) are different from those on the label of the type lot (81��50��� N, 136��14��� E) (Fig. 2, green star); however, other information, such as depth (3,700 ���3,800 m), date of collection (July 24, 1938), and station number (st. 101), is the same in both sources. The sample with Leptogyra bujnitzkii was collected during the forced drift of r/v Sadko, which was blocked by ice together with two ice-breakers, i/b Georgiy Sedov and i/b Malygin (Zubov 1940). The captain of the i/b Georgiy Sedov (Badygin 1950) gives coordinates of the convoy for July 23 and 25, 1938 in his memories (81��50.8��� N, 136��11��� E and 81��51.5��� N, 135��40��� E, respectively), which are very close to the location indicated on the label (Fig. 2C). Therefore, we conclude that they are correctly indicating type locality of this species. Leptogyra bujnitzkii is the first representative of the gastropod subclass Neomphaliones known from the Arctic Ocean. Representatives of the genus Leptogyra, like other members of the subclass, are known exclusively from habitats such as sunken wood or hydrothermal vents (Hess et al. 2008). Unfortunately, there is no information about the habitat of Leptogyra bujnitzkii. The collection site is located on the way of ���transpolar drift stream���: a route of travel of Siberian wood to Greenland and the American continent (Dyke et al. 1997). Bottom communities associated with sunken wood are known from several deep water regions of the extreme North of the Atlantic Ocean, such as from the deep water off Northern Iceland (War��n 1996; Ockelmann & Dinesen 2011) and eastern Greenland (Schulz et al. 2010), but there is no direct evidence about the presence of such biocoenoses from the high Arctic Basin, which remains poorly studied. As there are no known geothermal areas around the type locality of Leptogyra bujnitzkii, we hypothesize that sunken wood is the most probable habitat for this species. *mean values **measured from published picture ���-��� ��� no data based on Marshall 1988, War��n & Bouchet, 1993, 2009 and original data, Published as part of Krol, Ekaterina N. & Nekhaev, Ivan O., 2020, Redescription of Leptogyra bujnitzkii (Gorbunov, 1946) comb. nov., the first representative of the gastropod subclass Neomphaliones from the high Arctic, pp. 446-450 in Zootaxa 4759 (3) on pages 446-449, DOI: 10.11646/zootaxa.4759.3.13, http://zenodo.org/record/3741156, {"references":["Gorbunov, G. P. (1946 a) Bottom life of the Novosiberian shoalwaters and the central part of the Arctic Ocean. In: Gorbunov, G. P. & Ushakov, P. V. (Eds.), Proceedings of the drifting expedition of Glavsevmorput on ice-breaker \" G. Sedov \". Vol. 3. Biology. Glavsevmorput Publ., Moscow, Leningrad, pp. 30 - 136.","Gorbunov, G. P. (1946 b) New and interesting species of Mollusa and Brachiopoda from the Arctic Ocean. In: Gorbunov, G. P. & Ushakov, P. V. (Eds.), Proceedings of the drifting expedition of Glavsevmorput on ice-breaker \" G. Sedov \". Vol. 3. Biology. Glavsevmorput Publ., Moscow, Leningrad, pp. 308 - 322.","Kantor, Y. I. & Sysoev, A. V. (2006) Marine and brackish water Gastropoda of Russia and adjacent countries: an illustrated catalogue. KMK Scientific Press Ltd., Moscow, 371 pp.","Bush, K. J. (1897) Revision of the marine gastropods referred to Cyclostrema, Adeorbis, Vitrinella and realted genera with dexriptions of some new genera and species belonging to the Atlantic fauna of America. Transactions of the Connecticut Academy of Arts and Sciences, 10, 97 - 144.","Marshall, B. A. (1988) Skeneidae, Vitrinellidae and Orbitestellidae (Mollusca: Gastropoda) associated with biogenic substrata from bathyal depths off New Zealand and New South Wales. Journal of Natural History, 22, 949 - 1004. https: // doi. org / 10.1080 / 00222938800770631","Bouchet, P. & Waren, A. (1993) Revision of the northeast Atlantic bathyal and abyssal Mesogastropoda. Bollettino Malacologico Supplement, 3, 579 - 840. https: // doi. org / 10.5962 / bhl. title. 140732","Waren, A. & Bouchet, P. (2009) New gastropods from deep-sea hydrocarbon seeps off West Africa. Deep-Sea Research Part II: Topical Studies in Oceanography, 56, 2326 - 2349. https: // doi. org / 10.1016 / j. dsr 2.2009.04.013","Hess, M., Beck, F., Gensler, H., Kano, Y., Kiel, S. & Haszprunar, G. (2008) Microanatomy, shell structre and molecular phylogeny of Leptogyra, Xyleptogyra and Leptogyropsis (Gastropoda: Neomphalida: Melanodrymiidae) from sunken wood. Journal of Molluscan Studies, 74, 383 - 401. https: // doi. org / 10.1093 / mollus / eyn 030","Zubov, N. N. (1940) The drift of the ice-breaker Sedov. Nature, 145, 533 - 539. https: // doi. org / 10.1038 / 145533 a 0","Badygin, K. (1950) Three wintering in the Arctic ice. Molodaya Gvardia, Moscow, 543 pp.","Dyke, A. S., England, J., Reimnitz, E. & Jette, H. (1997) Changes in driftwood delivery to the Canadian Arctic Archipelago: The hypothesis of postglacial oscillations of the transpolar drift. Arctic, 50, 1 - 16. https: // doi. org / 10.14430 / arctic 1086","Waren, A. (1996) New and little known Mollusca from Iceland and Scandinavia. Part 3. Sarsia, 81, 197 - 245. https: // doi. org / 10.1080 / 00364827.1996.10413622","Ockelmann, K. W. & Dinesen, G. E. (2011) Life on wood - the carnivorous deep-sea mussel Idas argenteus (Bathymodiolinae, Mytilidae, Bivalvia). Marine Biology Research, 7, 71 - 84. https: // doi. org / 10.1080 / 17451001003714504","Schulz, M., Bergmann, M., Juterzenka, K. von & Soltwedel, T. (2010) Colonisation of hard substrata along a channel system in the deep Greenland Sea. Polar Biology, 33, 1359 - 1369. https: // doi. org / 10.1007 / s 00300 - 010 - 0825 - 9"]}

Recently discovered hydrothermal vent fields on the East Scotia Ridge (ESR, 56–60°S, 30°W), Southern Ocean, and the South West Indian Ridge (SWIR, 37°S 49°E), Indian Ocean, host two closely related new species of peltospirid gastropods. Morphological and molecular (mitochondrial cytochrome c oxidase subunit I, COI) characterization justify the erection of Gigantopelta gen. nov. within the Peltospiroidae with two new species, Gigantopelta chessoia sp. nov. from ESR and Gigantopelta aegis sp. nov. from SWIR. They attain an extremely large size for the clade Neomphalina, reaching 45.7 mm in shell diameter. The oesophageal gland of both species is markedly enlarged. Gigantopelta aegis has a thick sulphide coating on both the shell and the operculum of unknown function. The analysis of a 579-bp fragment of the COI gene resulted in 19–28% pairwise distance between Gigantopelta and six other genera in Peltospiridae, whereas the range amongst those six genera was 12–28%. The COI divergence between the two newly described species of Gigantopelta was 4.43%. Population genetics analyses using COI (370 bp) of 30 individuals of each species confirmed their genetic isolation and indicate recent rapid demographic expansion in both species

Humptulipsia nobuharai sp. nov. (Fig. 7 G, J–M) Type locality and strata: Sada Limestone, Shikoku, Japan; Campanian-Maastrichian (Late Cretaceous); for details see Nobuhara et al. (2008). Holotype: UMUT MM 31170, two moderately well-preserved whorls 26.8 mm high and 15.4 mm wide. Paratypes: UMUT MM 31230, adult specimen, UMUT MM 31171, UMUT MM 31172, two juvenile shells, UMUT MM 31173 fragmentary specimen displaying the humptulipsid slit on the shell base. Additional material: Many unprepared specimens from the type locality. This gastropod occurs in mass accumulations at the type locality. Diagnosis. Tall shell with largest whorl diameter in mid-flank. Adult shell smooth apart from prosocyrt growth. Shell base with narrow slit in its abapical portion. Description. Tall shell with largest whorl diameter at mid-whorl. Protoconch and juvenile teleoconch unknown. Adult shell smooth apart from prosocyrt growth lines. Shell base with narrow slit in its abapical portion. Suture weakly incised. Aperture poorly preserved, drop-shaped. Remarks. Humptulipsia nobuharai is the third species of Humptulipsia described so far. The type species H. raui is known from Eocene/Oligocene hydrocarbon seeps in Washington state (Kiel 2008) and differs from H. nobuharai in having a much wider slit that is located much higher on the whorls. Humptulipsia macsotayi Kiel et al., 2010 described from Hauterivian (Early Cretaceous) presumed seep carbonates in southeastern France (Kiel et al. 2010) differs from H. nobuharai by being ornamented throughout the entire shell ontogeny. We include Humptulipsia in the Hokkaidoconchidae due to the hokkaidoconchid-like ornamentation of the juvenile shell in H. raui (see Fig. 1.9 in Kiel 2008 and Fig. 7 H herein). A slit similar to that of Humptulipsia is present in the members of family Pseudolividae de Gregorio, 1880, which differ, however, in ornamentation style of the early whorls (see e.g., Pacaud & Schnetler 1999) and are known in the fossil record from Maastrichtian, Late Cretaceous (Kaim & Beisel 2005). Etymology. For Takami Nobuhara who made the field trip to the Sada Limestone deposit possible., Published as part of Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014, Mollusks from late Mesozoic seep deposits, chiefly in California, pp. 401-440 in Zootaxa 3861 (5) on pages 417-418, DOI: 10.11646/zootaxa.3861.5.1, http://zenodo.org/record/252462, {"references":["Nobuhara, T., Onda, D., Kikuchi, N., Kondo, Y., Matsubara, K., Amano, K., Jenkins, R. G., Hikida, Y. & Majima, R. (2008) Lithofacies and fossil assemblages of the Upper Cretaceous Sada Limestone, Shimanto City, Kochi Prefcture, Shikoku, Japan. Fossils, The Japanese Journal of the Palaeontological Society of Japan, 84, 47 - 60.","Gregorio, A. de (1880) Fauna di S. Giovanni Ilarione (Parisiano). Parte 1, Cefalopodi e Gasteropodi, fasc. 1. Montaine, Palermo, 106 pp.","Pacaud, J. - M. & Schnetler, K. I. (1999) Revision of the family Pseudolividae from the Paleocene of West Greenland and Denmark. Bulletin of the Geological Society of Denmark, 46, 53 - 67.","Kaim, A. & Beisel, A. L. (2005) Mesozoic gastropods from Siberia and Timan (Russia). Part 2: Neogastropoda and Heterobranchia. Polish Polar Research, 26, 41 - 64."]}