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VENUS {Jap. ][]ur. Ma]ac,> Hva - Vol. 54, No, 4 (. 1995), 279 293

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A Revision of Systematic Position of Genus Leueotina

(Gastropoda: Heterostropha)

Shigeo HoRI and Eiji TsuCHIDA (Tokyo University of Fisheries, 4-S-7, Konan, Minato-ku, Tokyo 108, and Ocean Research Institute, University of Tokyo, Nakano-ku, Tokyo 164)

Abstract: Leucotina was established at first as a genus of the family Acteonidae, but later it had been allocated in the family Pyramidellidae. But, Ponder (1987) speculated that this genus may belong to the family Amathinidae based on shell, though soft part characters were not comfirmed. The present investigation on net only shell but also soft part charac- ters of two Leucoirina species including the type species of this genus concluded that this genus is decidedly a member of the Amathinidae.

Introduction

Leucotina is a group of small gastropod living on sandy bottom in the Pacific area

including Japan, China, and Australia. Ecology of this gastropod has hardly been known to date. However, since Coleman (1981) reported that one species of this genus attaches

to a large bivalve, probably Glycymeris, it is possible that this genus is ectoparasitic on such large bivalves. The genus Leucotina was established by Adams (1860) in the family Acteonidae based on ovate, ventricose shell with spiral keels and punctated interspaces,

and a hidden oblique columellar fold. This genus has subsequently been regarded as a subgenus of the genus Kleinella of the family PyTamidellidae (e.g. Thiele, 1930; Wenz, 1940). Later, when Ponder (1987) established the family Amathinidae based on Amathina tricarinata (Linnaeus, 1767), which is cornmon to the superfamily Pyramidelloidea in soft

part characters, he speculated that this genus may also belong to the family Amathinidae. This is because the shell of the type species of this genus, L. niphonensis A. Adams,

1860 is closely similar to that of iselica which was transferred into the Amathinidae based

on the similarity of soft part characters. Vaught (1989) and Fukuda et al. (1992) followed Pender's assignment, and listed this genus in the Amathinidae. However, the anatomical

confirmation of the allocation of this genus in the Amathinidae has not been attempted

to date. = In this study, we re-investigated the type specimens of L. niphonensis, and L. dianae

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(A. Adams, 1855) deposited in The British Museurn (Natural History), London. Since this

revision revealed that the former species should be synonymized with the latter, the type

species of this genus is now L. dianae. Further, we could inyestigate shell and soft part of L. dianae and L. digitatis (Dall & Bartsch, 1906) collected by ourselyes. The present investigation revealed that the characters of this genus is clearly different from those of

other rnembers of the family Pyramidellidae, but agree with those of the Amathinidae in-

troduced by Ponder (1987).

Materials and methods

The specimens used in this study weTe all preserved in 70% alcohol. The shells of

all specimens for dissection were dissolved by a solution of diluted hydrochloric acid. Exter-

nal features of head-foot in living condition was inyestigated under a stereomicroscope.

All soft part anatomy was accomplished under a stereomicroscope and a biological micro-

scope, but not by sectioned material at all. Terminology used in this study adopts chiefly Ponder (1987). In case that no appropri-

ate term seems to be available, new ones are here proposed. In the taxonomic descriptions, the abbreviations of anatomical terminology, which is all common to Figs. 12-20 and 25-29, will be arbitrarily inserted to help for referring textfigures.

The type species of Leucotina

Adams (1860) designated Leucotina niphonensis A. Adams, 1860 as the type species of the genus Leucotina. The range of infraspecific variation of shell of L. dianae (A. Adams, 185S) is rather large for shell length and shell width ratio, grade of swelling of each whorl, proponion of the body whorl, strength and width of spiral keels, among others (Figs. 1-11). Since the type specimens of L. niphonensis are young specirnens within an

infraspecific variation of L. dianae, L. niphonensis should be synonymized with L. dianae.

Taxonomy

Superfamily PYRAMIDELLOIDEA Gray, 1840 Family AMATHINIDAE Ponder, 1987

Genus Leueotina A. Adams, 1860

7ype species: Leucotina dianae (A. Adams, 1855) SheU: The shell is thick, ovate to oblong ovate. Strong spiral keels with longitudinal

striae in the interspaces on the whole surface of the shell.

(ipercutum: The operculutn is horny, paucispiral, and oyate. Headifbot: The cephalic tentacles are extended anteriorly. From the middle of the basal area of the cephalic tentacles, the mentum protrudes anteriorly. The dorsal area little behind the middle part of the foot is somewhat widened laterally and carries an operculum. M/antte cavity: Inner right lateral part of the mantle cayity, the dorsal ciliated strip and the ventral ciliated strip run posteriorly. Beneath the ventral ciliated strip the pallial

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gland is the ventral ciliated strip running posteriorly. The gill is located on the left part of the dorsal ciliated strip. The kidney is present in the slightly left area to the rnantle roof behind the gill. Central nervous system: The central nervous system is highly concentrated, and consists

of the circumoesophageal nerve ring and the visceral loop. The circurnoesophageal nerve

ring eonsists of following ganglia: Two cerebral ganglia, two pedal ganglia, and the left and the right pleural ganglia. The visceral loop tracks the following pathway: Right pleural ganglion-supraoesophageal ganglion-visceral ganglion-suboesophageal ganglion-left pleural ganglion. Anterior alimentac), canal: The long proboscis sheath is followed by the buccal pump with no blind-sac. Although there is neither radula nor stylet, a chitinous valve-like structure is present in the anterior part of the buccal purnp. Genitat system: Glandular part of the genital system consists of the hermaphrodite gland, the posterior mucous gland, and the anterior mucous gland. The anterior part of the anterior mucous gland extends anteriorly to the mantle cayity floor. The copulatory apparatus is independent from the other part of the genital system and located in the cephal- ic haernocoel. The copulatory apparatus accords with the penis that is housed in the penial sheath, which passes beneath the cireumoesophageal nerve ring.

Leucotina dianae (A. Adams, 1855)

(Figs, 1-20)

Acteon dianae A. Adams, 18S5, p. 59; Habe, 1985, p. 11, pl, 2, fig. 3, Tbrnatella dianae: Reeve, 1865, pt. 4, fig, 19; Lischke, 1871, p, 171; Lischke, 1874, p. 76, Leucotina dianae: Tryon, 1893, p. 167, pl. 18, figs, 68, 69, 88, 89; Kuroda & Habe, 1971, p. 270, pl. 113, fig. 16; Tsuchida & Hori, 1992, p. 6, pl. 1, fig, 10; Fukuda et al., 1992, p. 73, pl, 23, fig. 335, Odostomia gigantea Dunker, 1877, p. 71. Acteon giganteus: Dunker, 1882, p, 160, pl, 2, figs. 8, 9, Leueotina gigantea: Pilsbry, 1893, p. 167, pl, 18, figs. 92, 93; Yokoyama, 1922, pp, 23-24, pl, 1, fig, 3; Nomura, 1938, p. 68, pl. 13, figs. 109a, 109b; Kira, 19S4, p. 188, pl. 68, fig. 17; Habe in Okada, 1965, p, IS8; Habe & Kosuge, 1967, p. 108, pl. 42, fig. 20; Kuroda & Habe, 1971, p. 270, pl. 113, fig, 15; Oyama, 1973, p. S9, pl. 17, fig. 20; Okutani, 1975, pp. 264; Hamatani in Okutani, 1986, p, 209. Leucotina niphonensis: A. Adams, 1860, p. 407; Habe, 198S, p. 11, pl, 3, figs, 7, 8, 7brnatella niphonensis: Reeve, 1865, pl, 4, fig. 16.

Materials examined: One living specimen from Otsuchi Bay, Iwate, depth of 52 m, collected

by E. Tsuchida, on August 22, 1985: 15.7x8.2mm.

Shell (Figs. 1-11): The shell is ovate (LIW =1.3-2.4), moderately thick, somewhat polished and milky white, covered by yellowish white periostracum. The protoconch is

helicoid, small, 150e heterostrophy, srnooth, and about lf2 of it is obliquely･immersed

in the first whorl of teleoconch (Fig. 12). The whorls of the teleoconch reaches seven

in number, with convex walls, and separated by well constricted sutures. The' outer surface

is marked by more or less distinct growth lines and flat spiral keels. The spiral keels are somewhat narrow at upper part of each whorl but become wider and nearly equal to each other on the middle to lower part. The number of the spiral keels is six to nine

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Hori & Tsuchida: A Revision of Systematic Position of Genus Leucotina 283

on the first to second whorls, seven to eleven on the third to fifth whorls, ten to twelve

on sixth to eighth whorls, and nine to 15 on the base. The interspaces of the spiral keel

is slightly irregular to each other, nearly equal to the spiral keel or narroWer than that,

and sculptured by distinct fine longitudinal lirae. The body whorl occupies 56-88{Vb of

the shell length, with convex periphery. The urnbilicus is wide. Aperture is auriculate oval, and occupies 36-64M of the shell length. The columella is somewhat thick and nearly

straight, possessing an obsolete oblique columellar fold at its upper part. The inner wall

is covered by a thin callus. The outer lip is thick and smooth, but denticulate in accordance

with spiral keels. The inner surface of the whorls is not sculptured.

(lpercutum (Fig. 13): The operculum is somewhat thick, and rhombic oblong in shape with somewhat coarse growth lines and no sculpture on the inner side. The color is translu- cent yellowish brown, but becomes gradually paler toward the margin. Head:fbot (Figs. 14, 15): The exposed part is pale orange in fixed specimen, presumably

translucent white in living condition. The cephalic tentacles(ct) are short, nearly trianguSar,

grooved along outer lateral sides. Although the eye$ (e) are set on the inner side of the

base of the cephalic tentacles, they are ernbedded in the epitheliurn, so that they cannot

be seen frorn outer surface at all in fixed specimen. The mentum(m) is trapezoid, and

its anterior part is longitudinally grooved. The proboscis pore is situated on the basal part of the grooye. The anterior end of the foot is truncated. The posterior end of the foot is rounded. The sole (so) of the foot possesses no visible pedal mucous gland opening. Mantte cavity (Figs. 14, 15): The mantle cavity reaches about 1!3 of the shell Iength,

and its width is about 215 of the mantle length. The dorsal and the ventral ciliated

strips(dcs, vcs) are rather wide and flat. Although both ciliated strips reach to nearly

posterior distal part of the mantle cavity, they do not join to each other at their posterior ends. The pallial gland(pgl) is narrow, long, and pale purple-brown. The area between these two ciliated strips is smoothly membranous. The gill (g) is wide, extended on the anterior middle part of the mantle roof. It is not a true ctenidium, but a secondary gill

Figs. 1-11. Leucotina dianae, vte/ ti{. SL == shell length, SW= shell width. 1, 2. Syntype specimens of L. niphonensis Mino-Shima (= Mishima Island, Yamaguchi), 63 fathoms, BM (NH) 1878.1,28,569 (A specimen from the Straits of Korea is not available). L. niphonensis a L(E'dayEtzkuaf4ga)ee pt)kweZts[. 1, SL=3,1 mm, SW=2.3 rnm; 2. SL=3.3 mm, SW=2.6 mm; 3. 0ff Wakamatsu, Hibiki-Nada, S, Hori coll. SL = 4.5 mm, SW = 2.9 rnm; 4, Off Naminosuke Island, Otsuchi Bay, Iwate, depth of 63 m, E. Tsuchida coll. SL=7,S mm, SW=4,3 mrn; S. Off Wakamatsu, Hibiki-Nada, S, Hori coll. SL = 12.0 mm, SW = 6,3 mm; 6. The specimen dissected for this study: Off Cape Nagasaki, Otsuchi Bay, Iwate, depth of 52 m, E. Tsuchida coll. 7tsfi"fiTemafidl:l[]MLkmatts. SL=IS,7 mm, SW=8.2 mm; 7. Holo- type specimen of L. dianae from Bay of Jedo (=Tokyo Bay), BM (NH) 199S174, y}E1 tilO']-u"ffrtec7tsl,. SL := 17,O mm, SW =9,O mm; 8, 9, Kii, NSMT-Mo 50754, 8. SL=26.0 mm, SW == 11.0 mmi 9, SL=29.0 mm, SW=12.0 mm; 10, 11. Isshiki, Aichi, NSMT-Mo 507S3, 10, SL= 29.5 mm, SW=IS.O mm; 11. SL=37.0 rnm, SW=18,Ornm.

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po so

ctx' sgsfs"'''''t aa !tt''' - '//'''.;'tt'.,/tttt't'' f' ''tt/t'.-'dcs';.Itt,lt-/-･Z･1:t: 9 t ,:.:tt.//':,-'./.,?;tt':;'ii'vcs El I ''lt.-;1-･' .}kg.li.,. t1L1:AeT:-.t'[;t''';t.t.ttlt-:.f''l,pgl rN... pVs- 1 ''''' -. r x.x"), ,lt'/･i"'''' t". s'i,ajXL,, /ttl:-L.r t'/tt''iJi'',l,. ':.tt't/'YJ.--,wo 1 K"x :Lf';'-1lt'r'am 1, ･'1L mg k---, .Y'･･, t. 'l'''' .tttltt/-. ]; .'xi'2 tr.. - 15

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Hori & Tsuchida: A Revision of Systematic Position of Genus Leucotina 285

that consists of many thin strings which are formed by vesicles arranged at right angle

to the longitudinal axis of the mantle cavity. The left half of mantle cavity fioor is o ¢ cupied

by an epithelium which covers the cephalic haemocoel. On the right anterier part of it, the anterior aorta(aa) forms a prominent longitudinal ridge, The right half of the mantle cavity floor is occupied by large and long anterior mucous gland(amg). The kidney(k)

is pale orange-yellow, and reaches about 215 of the mantle length. Posterior to the left side of the kidney, ovate pericardium(pc) is loeated. The pallial vein(pv) is originated from the left side of the gill and runs along the left side of the kidney and is extended posteriorly to the pericardium. The left part of the pallial vein becomes a thin translucent

membranous area.

Central nervous system (Fig. 16): The cerebral gangiion (cg) is large and oval, attaining about O.5 mm in length and O.3 mrn in width. On the anterior end of this ganglion, much srnaller tentacular ganglion (tg) and a thin nerve arise. From the tentacular ganglion, major tentacular neTve and another thin nerve are extended anteriorly. Each cerebral gan- glion is connected with each other by a narrow commissure of which length is about O.lmm

and width is about O.05 mm. The pedal ganglia(pg) is circular, slightly smaller than the cerebral ganglion. The anterior part of this ganglion possesses at least four nerves which run anteriorly. Each pedal ganglion is also connected with each otheT by a commissure. Between cerebral and pedal ganglia are connected dorso-ventrally by long connectives, which attain about O.4 mm in length and about O.05 mm in width. The right pleural ganglion (rpg) is globular, about 1!4 of the length of the cerebral ganglion in diameter. A very thin nerve arises from its postero-dorsal part. The left pleural ganglion (lpg) is oblong fusiform, about 113 of the cerebral ganglion in length and about 115 in width. Each pleural ganglion

:E Figs. 12-20.Leucotina dianae. ? I: / tf I . 12. Lateral view of protoconch. n:tb'k'Mljmi, Scale==O.2 mm; 13, Inner side of operculllm. esOVgwh. Scale=1 mm; 14, Dorsal view of anterior part with shell removed. uereryt?FkZlikftsfiflzzWtu, Scale=1 mm; IS. Dorsal view of mantle cavity

opened. t[Jma L7ti Y+･ffH!'ilfde, Scale = 1 mm. aa, anterier aorta, WiJttJltutH)it; amg, anterior mucous gland. cr/r"lii'flifi*; ct, cephalic '"ViP,IIma'E･ur; tentacle. li]easfidifO; dcs, dorsal ciliated strip. g, gill, taE; k, kidney, "fiHes; m, mentum. Nnig"+k; pc, pericardium. ,L,ti; pgl, pallial gland, 5dF:nR; pmg, posterior mucous gland, tft\hi'ftinM; pp, proboscis pore, [IPtacaLllge; pv, pal!ial vein, SrFgfi3-k; so, sole, methi; ycs, ventral ciliated strip. HstiP.11ma'EW, 16. Dorsal view of central nervous system. 4iNi(.ptkEX'l8fi, Scale=O,5 rnm; 17. An- terior alimentary canal. NtLev'fif't,e5. Scale= 1 mm; 18, Semi-diagrammatic drawing of mouth region longitudinally opened. wrl:WmaLkLIS (\waikpa). Scale ==O,S mm. apb, anterior end of proboscis. nuigrifii,,X; bp, buccal pump, nXrstvailX; cg, cerebral ganglion. Hfipti$ipm; ev, chitinous valve-like structure. keLYtaci)"iAltntnf" ; lpg, left pleural ganglion. ELH,ljptKpm; rnr, mouth region. [1ss; op, oral papilla, l ltth,fi'Xsc; osn, osphradial nerve. uftkZ"fiptff; pb, proboscis,nnto; ps, proboscis sheath. LIUtowt; rpg, right pleural ganglion, tifP.ijpmSipm; sbg, suboesophageal ganglien. ftM'Fk"SIMfi; sog, supraoesophageal ganglion. ftnLptS\pm; tg, tentacular ganglion. twfikltWfi; vg, visceral ganglion. NEGpt$'Epm . 19, Dorsal view of arrangement of genital accessory glands, tir.fui･ttsHltO)tseR<"Hliwh), Scale=S mm. 20. Copulatory apparatus. dtitu"th", Scale=O.1 mrn. amg, anterior mucous gland. rkfiN?diHk; pe, penis. Fft-g; pes, penial sheath, Fk'ig'wr; pmg, posterior mucous gland. ikllhi&"k; yd, vas deferens. wtreF;.

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is connected with the cerebral and pedal ganglia respectively by the connectives. Of these connectives, the ones with the cerebral ganglia are very short and about O.05 mrn in width. The one between the right pleural ganglion and the pedal ganglion is about O.3 mm in length and O.05 mm in width, while the one between the left pleural ganglion and the pedal ganglion is O,1 mm in length and O.05 mm in width. The supraoesophageal gan- glion (sog) is elliptic, about lf2 of the cerebral ganglion in length and about 113 in width.

The osphradial nerve(osn) arises from the left dorsal part of this ganglion. The visceral ganglion(vg) is somewhat spherical, reaches about 112 of the cerebral ganglion in length and width, One major nerve and two small nerves arise frorn the right posterior part of this ganglion. Between the right pleural ganglion and the supraoesophageal ganglion, and between the supraoesophageal ganglion and the visceral ganglion are connected by short and indistinct connectives. The suboesophageal(sbg) ganglion is oblong fusiform, about lf2 of the cerebral ganglion in length and about 1/5 in width. A tiny nerve arises from the anterior left part of this ganglion. The connective between this ganglion and the visceral ganglion is about O.2 mm in length and about O.OS mm in width, while that between this ganglion and the left pleural ganglion is about O.1 mm in length and about O.OS mm in width.Anterior

alimentat:y canal (Figs. 17, 18): The proboscis sheath(ps), in retracted condition,

is contained into the cephalic haemocoel, reaching about 1.5 cm in length and O.4 mm

in maximum width. It arises from the proboscis pore on the mentum, passing through the circumoesophageal nerve ring, and it is connected with the mouth region(mr) at its

posterior end. The wall of the proboscis sheath is thick, composed by the inner layer

of circular muscles and the outer layer of longitudinal muscles. Inner wall of the mouth

region possesses several oral papillae(op) of which length is about O.2 mm. The chitinous valve-like structure (cv) is located in the inner side of the mouth region irnmediately behind

the oral papilae, This part possesses many thin longitudinal grooves on its inner surface, and it reaches about O.3 mm in length, The buccal pump(bp) behind the mouth region

has a thick museular wal1, reaches about 7 mm in length and about O.3 mm in maximum

width. The posterior end of the buccal pump continues to the proboscis(pb) of which wall is thinner than that of the buccal pump. It reaches at least 1 cm in length and about

O.3 mm in width. Genital opnystem (Figs. 19, 20): The hermaphrodite gland in pale yellowish orange color runs along the digestive gland on the columellar side of the upper yisceral coil. The anterior end of this gland is connected with the hermaphrodite duct. On the outer side of the yisceral coil, the posterior mucous gland(prng) is located. It is yellowish white, reaches to about 20 mm in length and 6 mm in width. The anterior mucous gland (amg) in translu- cent grayish white lies on the convex side of the posterior mucous gland as a mid-dorsal strip along the latter. The anterior part of the anterior mucous gland extends anteriorly along the right part of the mantle cavity floor, reaching behind the neck. This part contains the comrnon genital duct, and it occupies the right half of the mantle cayity floor. The copulatory appara'tus reaches beneath of the little behind the level of the nerve ring. The

penial sheath(pes) is slender, with the vas deferens(yd) in its dorsal wall for its whole length, and it is spotted by numerous yellowish brown to green-brown tiny ovate glands in its inner surface. The penis(pe) is slender whip-like, about 2 mm in length and O.1

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O.1 mm in width, and it gradually tapers toward its anterior end. Although the penial duct passes through the center of the penis, it becomes indistinct on the posterior part of the penis. The penis and the penial sheath are connected with each other at their posteri-

or distal ends.

7)epe tocality: Tokyo Bay.

Geographical distribution: Otsuchi Bay south to Kyushu (Habe, 1961).

Hbbitat: This species is found on a muddy sand bottom of depth of 10 to 50 m in depth

(Kuroda & Habe, 1971).

Leucotina digitalis (Dall & Bartsch, 1906)

(Figs. 21--29)

llyramidella (Actaeopyramis) digitatis Dall & Bartsch, 1906, pp. 331-332, pl. 19, fig. 6. Materials examined: Two living specimens from off Banda, Tateyama Bay, collected

by S. Hori, on June 3, 1992; 7.0x3.0mm in size.

SheU (Figs. 21-24): The shell is oblong ovate (LfW = 1.7-2.1), thick, somewhat polished, and milky white to white. The protoconch is helicoid, small, 150" heterostrophy, smooth, and about 2/3 of it is obliquely immersed in the first whorl of the teleoconch (Fig. 25).

The whorls of the teleoconch reaches six in number, with conyex walls, and separated by

"i'"i' Figs. 21-24. Leucotina digitatis, ij VL7 I:E? ti d . SL= shell length, SW=shell width.

21, 22, Off Wakamatsu, Hibiki-Nada, S. Hori coll. 21. SL = 3.3 mm, SW = 1,9 mm; 22. SL=6.8 mm, SW=3.0 mm; 23, 24, Fukura, Awaji Island, NSMT-Mo 2524,

23. SL=12.0 mm, SW=6.1 mm; 24. SL=15.0 mm, SW=7.0 mm.

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m PP

一 29

FigS．25 − 29。 Leucotina digitalis．サ サ ク レ マ キ モ ノ ガ イ．

25．Lateral view of protoconch ．胎 殼 側 面 ．Scale ＝0 ．l mm ； 26． Inner side of opercu ・ の ＝ lum．蓋 内面 ． Sca且e 05 mm ； 27、 Head in liying condition ．頭 部 （生 時 ）． Scale ＝ 1mm ，

ct， cephalic tentacle ．豆頁部触 角 ； e ， eye ．眼 ； m ， mentum ．口 吻 基 板 ； pp ， proboscis pore．口 吻 開 冂 部 ． 28。Alimentary canai ．消 化 管 前 部 ． Scale＝O ．5 mm ． ・口 部 神 経 節 bp buccal bg ， buccal ganglion ； ， pump ．口 部 吸 引 器 ； cpt crop ．嘆 嚢 ； mr mouth region ，口 部 ； oe oesophagus orm oesophagus retractor muscle ． ， ．食道 ； ， ． ． 食 道 牽 引 筋 L．1吻 ； pb ，proboscis． ； prm ， primary proboscis retractor muscle ，第 口 吻 ； sheath 牽 引 筋 ps ， proboscis ．口 吻 鞘 ； srm ，secondary proboscis retractor muscle 。 第 ：凵 吻牽 引 筋 ． 29．Copulatory apparatus ．交 接 器 ． Scale＝0 ．1 mm ． pe， penis．陰 茎 ； pes， penial sheath ．陰 茎 鞘 ； yd ， vas deferens．輪券肖管 ．

distinct and subconstricted sutures ． The outer surface is marked by somewhat distinct

lines and strong spiral keels． Of these spiral keels growth ， the upper most one is narrower

than the other ones ， and the others are nearly equal to each other in width ．The number

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Hori & Tsuchida: A Revision of Systematic Position of Genus Leucotina 289

of the spiral keels is five on the first whorl, five to eight on the second to fifth whorls,

seven to ten on sixth whorl, and seven to nine on the base, The inrerspaces of the spiral

keels are more or less narrower than the keel, sculptured by distinct and strong longitudinal

lirae. The body whorl occupies 61-75glb of the shell length with convex periphery, The

umbilicus is somewhat wide. Aperture is auriculate oval, and occupies 40-53CVb of the

shell length. The columella is somewhat thick and nearly straight, possessing an obsolete

oblique columellar fold which cannot be seen from the ventral side of the shell. The inner

wall is covered by a thin callus. The outer lip is thick. The inner surface of the whorls

is net sculptured.

Ctpercutum (Fig. 26): The operculum is more or less thick, oblong in shape, possessing somewhat coarse growth lines and no sculpture on the inner side. The color is translucent yellew, but becomes gradually paler toward the margin. Hlead-foot (Fig. 27): The exposed part is translucently yellowish white, spotted by rnany orange to brown spots all over. The inner and outer lateral parts of the cephalic tentacles and the lateral sides of the propodium are orange in color. The cephalic tentacles are somewhat rectangular, laterally grooved, with blunt tips. The eyes are distinct, set

on the inner side of the base of the cephalic tentacles. The mentum is heart-shaped, and

about anterior half of the mentum is longitudinally grooved. The proboscis pore is situated on the base of this groove. The foot is truncated at its anterior end. There is no visible pedal mucous gland opening. Mantte cavity (fixed specimens): The rnantle cavity is moderately long, reaching to

about 215 of the shell length, and its width is about 1/3 of the mantle cavity length.

The dorsal and ventral ciliated strips are somewhat flat, and they continue to nearly the

posterior end of the mantle cavity, but are connected with each other at their posterior ends. The gill spreads on the anterior middle part of the mantle roof. The pallial gland in pale yellowish orange color lies for nearly whole length of the mantle ¢ avity. The anterior aorta is prominent. The kidney is pale orange-yellow, about 215 of the mantle length, The right half of the mantle cavity floor is occupied by large and long mucous gland.

Anterior atimentary canal (Fig. 28: fixed specimens): The proboscis sheath is long and slender, reaches about 1 cm in length, About anterior 116 part of the proboscis is stout, and its width is O.3 mm. About 15 thin secondary proboscis retractor muscles(srm)

arise on the outer surface of this part. About posterior 5/6 part of the proboscis sheath becomes narrower, of which width is O.1 mm. The buccal pump reaches to O.6 mm in length and O.2 mm in width. The proboscis is 4 mm in length and O.13 mm in width.

Only the layer of the longitudinal muscles is obviously seen on the wall of the proboscis. The proboscis is followed by short oesophagus (oe), which is O,3 mm in length and O.13 mm in width. The posterior end of the oesophagus suddenly expands and becomes an ovate

bag-like crop(cp). Its wall is thin, and reaches 1.1 mm in length and O.5 mm in width.

The primary proboscis retractor muscle (prm) connects the anterior part of the proboscis sheath with the circular muscle. The middle part of this muscle is connected by very short oesophagus retractor muscle(orm). The buccal ganglia(bg) are located on this muscle. Another end of the oesophagus retractor muscle is attached by junction of the proboscis and the oesophagus. Anterior to the junction of the oesophagus retractor muscle on the proboscis retractor muscle is divided into some filaments reaching to the proboscis sheath.

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Genital opnstem Cfixed specimens): The albumen gland is pale yellow, and reaches to about 3 rnm in length and 1.5 mm in width. The mucous gland is translucent grayish white. Its posterior part rides on the albumen gland as a mid-dorsal strip. Wide anterior part of it extends from the somewhat posterior part of the mantle cavity floor behind the neck, and it occupies the right half of the mantle cavity floor. Ovate seminal receptacle

is situated on the right lateral part of the posterior end of the mantle cavity. It reaches about O.2 mrn in diameter. The penial sheath possesses the vas deferens on its wal1, connected with the penis at its posterior end. The penis is slender whip-like with the penial duct in its center, and it reaches about 1 mm in length and O.05 mm in width (Fig. 29).

``Japan". 7Jype tocatity: .

Geographical distribution: Boso Peninsula, Awaji Island, and Hibiki-Nada.

Discussion

This study at first revealed that the type species of the genus Leucotina, L, niphonensis is a junior synonym of L. dianae. Second.arily, investigations on the newly designated type

species and another species assured that Leucotina belongs to the family Amathinidae as

was suggested by Ponder (1987). The fundamental plan of the organs in the mant!e cavity, especially the position ef the gill, is one of the most important character to prove that this genus belongs to the Amathinidae. Ponder (1987) pointed that the gill of the family Arnathinidae is located on the left to the dorsal ciliated strip unlike several pyramidellids of which gill is situated on the right. This genus has no pigmented mantle organ [=hypobranchial gland by Ponder (1987)] on the middle part of the mantle roof as in the Amathinidae but unlike in the Pyramidellidae (Ponder, 1987). The mouth region of this genus has the oral papMae (observed only in L. dianae) as in the Amathina tricarinata (Linnaeus, 1767) (Ponder, 1987) but no sucker unlike the Pyramidellidae (Fretter & Graham, 1949; Fretter, 1951; Ponder, 1987; Wise, 1993). The chitinous valve-like structure as in the Amathinidae (Ponder, 1987) is present behind the oral papillae in this genus (observed only on L. dianae) in contrast to the Pyramidellidae which has the stylet on this area (Fretter & Graham, 1949; Fretter, 1951; Maas, 1965; Ponder, 1987; Wise, 1993). In this genus, the posterior part of the rnouth region immediate- ly forms a simple tubular buccal pump with thick wall as in the Amathinidae (Ponder, 1987). The posterior part of the mouth region of the Pyramidellidae continues to the buccal pump via the buccal sac Sn which the stylet is contained. Further, the buccal pump of the Pyramidellidae is often divided into two, of which the posterior one becomes blind sac-like (Fretter & Graham, 1949; Maas, 1965; Ponder, 1987; Wise, 1993). The proboscis of this genus seems to correspond with the anterior section of the oesophagus of the Pyramidellidae as the depiction on the Amathinidae by Ponder (1987). The posterior part

of the proboscis of this genus possesses a bag-like crop as in A. tricarin, ata. Such a structuTe

is entirely absent in the Pyramidellidae. The plan of the accessory glands of the genital system differs between A. tricarinata and species of the Pyramidellidae. In A. tricarinata, a large gland is situated on the outer side of the visceral hump. Further, another gland runs as a mid-dorsal strip along the

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Hori & Tsuchida: A Revision of Systematic Position of Genus Leucotina 291

former, and its anterior part surrounding the common genital duct extends anteriorly along the right side of the mantle cavity (Ponder, 1987). He called the former gland the posterior

"mucous" ``mucous'' gland, and the latter gland the anterior gland. While in pyramidellids, outer side of the visceral coil has the albumen gland and the mucous gland which is situated on the outer side of the former and is sometimes divided into the anterior and posterior ones. The right side of the mantle cavity of pyramidellids possesses the prostate or the common genital gland (Fretter & Graham, 1949; Hori, pers. obs.). This genus has the plan of the accessory glands entirely the same to that of A. tricarinata. However, since

"mucous" the homogeneity of the posteriorlanterior gland by Ponder (1987) and the albumenlmucous gland of pyrarnidellids is unknown because of lack of histelogical investi- gation. This study adopted PondeT's terms. The penis of this genus runs beneath the circumoesophageal nerve ring as in the Amathinidae (Ponder, 1987) but unlike several pyramidellids of which penis passes through the cirumoesophageal nerve ring (Fretter & Graham, 1949; Fretter, 1951; Maas, 1964). This genus has the penial duct in the penis like Amathina tricarinata in contrast to the pyramidellids which has the penis with hae- mocoel or opened dorsal groove (Fretter & Graham, 1949; Fretter, 1951).

- Acknowleagments: We wish to express our deepest gratidude to Dr, Takashi Okutani, Professor

Emeritus, the Tokyo University of Fisheries, for critical reviewing this manuscript and valuable advices, We thank Dr, Susumu Segawa and Dr, Kotaro Tsuchiya for varieus advices and encouragement. We also wish thank Ms. Kathy Way, the collection rnanager of British Museum (Natural History), Lendon,

for the loan of the type specimens of Leucotina niphonensis and L. dianae, and Dr. Hiroshi Saito,

National Science Museum Tokyo, for the loan of specimens of L. dianae and L. digitalis under his care.

References

Adams, A. 1855. Monographs of Acteon and Solidula, two genera of gastropodous Mollusca with descriptions of several new species from the Cumingian collection. Aroc. ZooL Soc. London, part 22: S8-62. Adams, A. 1860. 0n some new genera and species of Mollusca from Japan. Ann. Mbg, Nbt. Hist,, Ser. 3, vol. 5 (29): 405-413. Colemam, N. 1981. Shells Alive!. Rigby, Adelaide, 96 pp. Dall, W, H. & P. Bartsch, 1906. Notes on Japanese, Indopacific, and American Pyramidellidae. Rroc,

U. S. ?Vllt. Mtls. 30:321-369, pls. 17-26. Dunker, W. 1877. Mollusca nonnulla nova maris Japonici. Adalak, BL 24:67-75,

Dunker, W. 1882, Ihdex Mblluseorum maris Jbponici. Cassel, vii+301 pp., pls. 1-16. Fretter, V. 19Sl. 7letrbonitla elegantissima (Montagu), a parasitic opisthobranch, four. Afur, BioL As- soc. U. K., 30:37-41. Fretter, V. & A. Graham, 1949. The structure and mode of life of the Pyramidellidae, parasitic opisthobranchs. Jbur. Mbr. BioL Assoc. U. K., 28:493-532, Fukuda, H., K. Mashino, & T. Sugimura. 1992. A review of the tnoUuscan founa of 7Ztmaguchi Pref. VVlestern Japan. Yamaguchi Museum, Yamaguchi, 99+xxvi pp., pls, 1-50. (in Japanese) Habe, T. 1961. Colored illttstrations of the shelts of .lapan, 2. Hoikusha, Osaka, ix + 182 + 46 pp., 66 pls. (in Japanese), Habe, T, 196S. in K. Okada. Nlew illustrated encyclopedia of thefauna of Jlapan. 2, Hokuryukan, Tokyo, 803pp, (in Japanese)

Habe, T. 1985, Illustrations of type specimens of the Japanese rnolluscan species described by A.

Adams and housed in the British Museum (Natural History). Spec. PubL Mbkaisima Mbr. BioL

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292 VENUS ； VoL 54 No 4 1995 ， ． （ ）

Stat．： 7 − 15．

S ． Kosuge ． 1967 of Japan 加 co ’or ． Hoikusha Osaka vii ＋ 194pp ． Habe ，T ＆ ， Common she ’ts ， ， （in Japanese） Hamatani ， L in T ， Okutani ．1986．1〃ust 砌 t’on qブ animats and ρ’ants ，物 ’lusca． Sekaibunkasya ， Tokyo，39gPP．（in Japanese）

Kira T 1954 〃 ustra ’ions the sheiis 砌 1 Hoikusha Osaka vii ＋ 240pp 71 ， ， ． Cotored げ qプ諏 ρ ． ． ， ， ．， Pls． （in Japa 鳳 ese ） Kuroda ， T ．＆ T ． Habe ．1971． Sea sheUs qプSagam’ β の ノ． Maruzen ， Tokyo ， xvi ＋ 741 ＋ 489 ＋ 51 pp ， 121pls ． Lischke， C ． E l871． Jaρanische Mee 厂es − Conch ア”en ． 2， Cassel，184 pp ．，14 pis．

− Lischke，C ．E ．1874． JapanischeMeeres Conchy〃en ． 3， Cassel， 123 pp ．， 9pls ．

von ： − Maas ， D ．1964．Uber Cuticularbildungen aln Penis Pyramidelliden．Zoo1 ．Anz ．，173 137 148． Maas ， D ．1965． Anatomische und histologische Untersuchungen am Mundappart der Pyramidelliden． Zeits． Morph ． Oko ’． 54 ： 566 − 642 ． Nonlura ， S．1938． The third report on Pyramidellidae based upon the specimens preserved in the

− − 互 coUection of the SaitoHo on Kai Museum ．Sa’ごo Ho on Ka ’Mus ．Res、BuU ． 6 ： レ 88， p！s， 1− 15．

Okutani T ．1975． Mo 伽 sca II ch ’ o 〃 1 ．lapan Ga 】（ken Tokyo 294 in Japanese ， ， efly〃 ， ， ， pp （ ） ’ Oyama ， K ．1973． Revision of Matajiro Yokoyama s type Mollusca from the Tertiary and Quartenary of the Kanto area ． Pa ’aeont ． Soe ．加 ． Sρ． Pap ．17 ： 148 PP ．，57 pls． Pilsbry， H ． A ．1893， Manual of Concho ’og γ， stntctura ’ and Systemat’‘ ． 15， Philadelphia，436 pp ．， Pls． 1−6L Ponder ， W ． F ．1987． The anatomy and relationships of the pyramidellacean limpet Amathina tricarinata − （Mollusca ： Gastropoda ）．」4sian Marine β ’ology 4 ； 1 34， ・ Reeve ， L ． A ．1865． Monograph of the ］rc）rnate 〃α ． Conchologia ／conica ． or 〃 ustrat ’ons q 〃 加 she ’ls q プ 〃10 ”useous an ’mals 。15， London ． − Thiele， J． 1929 1935． Handbuch der Sンsten1atiSchen Me ’chtie 厂kunde ． Jena， 1154 pp ．

＆ of marine mollusks of sea around Tsuchida ， E S ，Hori ， 1992 ，Fauna the Otsuchi Bay ， Iwate

Prefecture （3）HeterogastrQpoda ， Opisthobranchia and Scaphopoda ． Otsuchi Mar ． Res ． Cent ． Rep ． − 18 ： 1 23 ． （in Japanese ） Vaught ， K ． C ．1993− 4 c’a∬ ipication q〃 舵 制 πg ルfo〃usea ． American Malacologists， Inc．， Melboume ， xii ＋ 195 PP ． − Wenz ， W ．1940．1938 1944． Gastropoda ． Handbuch der P α ’aozoo ’og ’e ，6Berlin ，1639 ＋ 10 pp ． Wise ， J． B ．1993． Anatomy and functional morphology of the feeding structures of the ectoparas 孟tic

Boonea impre Pyramidellidae Ma ’ ’ ’α 35 1 ： 119 − B4 gastropod ∬ a （ ）． aco og ， （） ．

Yokoyama ， M ．1922． Fossils from Upper Musashino of Kazusa and Shimosa ． ノOur ． Co 〃， Sei．伽 ρ ． 一 − 砺 ’v ． τbkソo ， 44 （1）： 且 200， pls． 1 17。

要 約

．． マ キ モ ノ ガ イ 属 Leucotina は キ ジ ビ キ ガ イ 科 の 属 と し て 発 表 さ れ た 属 で あ る が ，長 ら くの 間 ト ウ ガ ・ ー タ ガ イ 科 の グ ル プ と し て 扱 わ れ て き た ． と こ ろ が ． P疋mder ｛1987 ｝は 貝殻 の 形 態 に 基 づ い て ，本属

が イ ソ チ ド リ ガ イ 科 に 属 す る こ と を提 唱 し た 。 し か し 本属 の 軟 体部 の 形 態 の 調 査 が 行 わ れ て い な か っ

は い か 一 こ で こ の （ A Adams 1855 マ キ た た め ，決定 的 な 確証 得 ら れ て な ） た c そ 度 ，Leucotina iicmae（ 、 ． ） ・ モ ノ ガ イ ，お よび ム，digitalis （Dall ＆ Bartsch、1906 ）サ サ ケ レ マ キ モ ノ ガ イ （新 称） を 貝殻 軟体 部 両 方 の に わ た っ て 調 査 し た ／．／そ の 結 果 ，そ れ ら は 以 ドの 点 に お い て ト ウ ガ タ ガ イ 科 と は 異 な り ，次 諸 点 に お い て 明 ら か に Ponder （1987）の 見 解 を支持 す る 、、す な わ ち ， 1． 鰓 は 背 側 繊毛 帯 の 左 側 に あ る ．， ． 2． 色素 外套 器官 は な い 、， 3． 冂 に 突 起 と キ チ ン 質 の 弁 が あ る 、． 部 ． 4． 口 部 ポ ン プ は 盲管状 と な ら ず に 単純 な 管 に な る ，．

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Position of Genus Leucotina 293 Hori ＆ Tsuchida ： ARevision of Systematic

・ の 後 部 は 帯 状 1・ 後 柵 列 泉の 黼 f． 生 殖 系 の 1攜 腺 は 後粘 irE腺 と 酬 腋 腺 か ら な り．fiiixf腋 腺 に ま で 伸 び る ， 中央 を 走 り ．前 部 は 共通 生 殖管 を囲 ん で 外 套 腔 前 庁 6． 陰 籌 は 内 部 に 陰 簑管 を も ち ．食道神 経 環 の 下側 を 走 る ． ‘：Ct A ． A ．Adams ，1860 で あ っ た が ． こ れ は 乙，‘liun （ な お 、マ キ モ ノ ガ イ 属 の 模 式種 は L ．niph θ nen ，vis こ と が か っ た ． Adams ，1855 ） マ キ モ ノ ガ イ の 幼 貝 で あ る 分 ．

【Received ： August 31，19951

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