The malacologicalsocietymalacological society of Japan
Res VENUS (jap. jour. Malac.) Vn]. 45, Ne,4 (1987):231 -244
pat13}e}kteigeeAIfRo?iifN= tz p ci . yopeF5 rv. -( -[) =?- s Jif ( F}, gt ze -e:- a) ew re vc L li
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Studies on the Kawamura Colleetion (Mollusea) Stored in the National Seience Museum, Tokyo IV. The Family Plaeunidae (Bivalvia) with Special Reference to their Ligament"
Akihiko MATsuKuMA
(National Science Museum, 3-23-1, Hyakunin-cho, Shinjuku-ku, Tokyo, 160>
A comprehensive survey of the Anomiacea based on the anatomy and shell
morphology, including the ligament, has been made by Yonge (1977). He eon-
eluded that the superfamily Anomiacea of the Pteriomorphia consists of two
different lines of deseent from primitive anomiacean stock: the Placunanomia-
Plaeuna (Placunidae) and Poclodesmus-Anomia-Enigmonia (Anomiidae) lines. The right valve of juvenile Placuna has a very small, degenerated byssal foramen,
However, Placuna species spend unattaehed free-living life, beeause the byssal
gland is barely functional during the pQstlarval stage (Yonge, 1977). They live
on the surface of mud flat lying on their right valve. They are eharacterized in
having very thin, strengly compressed, suborbicular, translucent shell with a
minute, closed, byssal noteh, diverging hinge-ridges and only one small, orbicular,
post･erior adduetor sear at the center of sheli (Kuroda, 1932). Hinge-teeth, an- terior adductor, hypobranchial gland, byssal apparatms and crural stalk have
disappeared. The shell of Placunidae is composed of foliated ea]eite and lacks a
complex crossed lamellar, aragonitic, inner layer which commonly occurs in speeies of Anomiidae, e.g. Anomia･ ephippium Linnaeus, 1758 (Taylor et al., 1969). The rather weak ligament ef Placuna consists of an amphidetic dorsal
ligament and a semieylindrieal internal ligament. They semicylindrical ligament
of the Placunidae is unique in the Pteriomorphia and is apparently similar to the
transverse ligament of the Mytilidae and Pinnidae among the Pteriomorphia and
the parivineular ligament of the Heterodonta. The morphology and function of
" Accepted: August 28, 1986
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232 VENUS: VoL 45, No.4(1987)
the Placuna ligament are diseussed in the following section.
Although fossil Placuua are known frem the Eocene to Oligocene of Europe
(Janssen, 1979) and nerthern Africa, living speeies are restricted to the tro- pieal Indo-West Paeific. Another genus of the Placunidae, i.e. Placzananomia.
Broderip, 1832, is confined to the tropical east Pacifie (Olsson, 196I; Bernard, 1983).
Linnaeus (1758) described Ano7nia plaeenta [=PIacuna placenta] from an "Pelago" uneertain loeality and then about ten species names have been pro-
posed by Philipsson (1788), Gmelin (1791), R6ding (1798), Lamarck (1819),
Blainville (1826), Gray (1849> and Sowerby (1871). They included many
synonyms and non-plaeunid species. For example, Lamarek (1819) enumera+ed
the following four speeies: Plac･Mna sella (Gmelin, 1791) [=:P. ephippium Phil-
ipsson, 1788], P. papyracea Lamarck, 1819 [=P. ephippiorm], P. placenta (Iin-
naeus, 1758), and P, peetinoides Lamarek, 1819. Lamarck (1819) cited figures
of Bruguiere et al. (1792, pl. 175, figs. 1-4) as references to P. pectinoides. The
figures illustrate thick, solid shells with the isedont-type hinge structure and
the posterior adductor scar placed near the postero-dorsal margin. These fea-
tures elearly prove that it should be placed in the genus Pl･icatuta Lamarck, 1801
of the Plicatulidae Watson, 1930,
Gray (1849) deseribed a new species of Placenta Philipsson, 1788 f'=Placuna
Lightfoot, 1786] and divided the genus Placenta into two greups, namely Placenta
eph-ippium-group and P. placenta-group. Accerding te Gray (1849) P, ephippt'um-
group contains P. ephippium, P. papyracea･ and P. Iincolnii Gray, 1849, and they
have hinge-ridges of nearly equal length rapidly diverging from one another,
The Placenta plaeenta-group ineludes only one species. In the shell ef P. placenta
the nymphs in the right valve gradually diverging from each other and the
posterier Iimb of nymphs is longer than the anterior, Plaeenta placenta-group
and P, ephippiu･m-group eorrespond with subgenera Plac2tna (s.s.) rLightfoot, 1786] and PIacuna (Ephippium) [R6ding, 17981 of medern authors, respectively.
Two Placuna species, namely Placuna･ (Placuna) placenta, (Linnaeus, 1758), and P. (Ephippium) ephippium (Philipsson, 1788) are found in the Kawamura
Collection, and an observation of Placuna ligament is inspired by t.he eNcellent
specimens in the collection. Another two species, viz. Placzana (Ephippium)
lineotnii (Gray, 1849) and Placitna (E.) lobata Sowerby, 1871 are stored in the
ordinary mollusk eollection of the Nationa! Science Museum, Tokyo and in
Dr. Horikoshi's private colleetion, Other species, e,g. Ptacuna pa･pyracea Lamarck, 1819, P. sella (Gmelin, 1791), P. poloniczam (R6ding, 1798) and P, quadrang2da (Philipsson, 1788), were considered te be synonyms of P. ephippium.
Acknowledgements:-This paper is dedieated to Dr. Tokubei Kuroda, an Honorary President of the Malaeologieal Society of Japan, in commemoration of his 100th anni-
versary of his birth. I am grateful to Professor Tadashige Habe of Tokai University,
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Matsukttma: Family Placunidae (Bivalvia) 233
Professor Takashi Okutani of Tokyo University of Fisheries, Dr. Frank R. Bernard
the ?acific Biologieal Station, Canada, and Dr. Katura Oyama, Toba Aquarium, foi
their fruitful diseussions and eomments on the subjeet for improving the manuseript.
Dr. Masuoki Horikoshi in Tokyo kindly allowed me to study his Ptacttna speeimens.
Ligarnent of the Placunidae
Shells of Placuna species are very thin and brittle. Their ventral margins
usually open narrowly and their ligament is small. The ligament of the Plaeuni-
dae is situated between the valves dersally and extends inwards on the reversed
V-shaped ridges Cnymphs) of the right valve. It consists of two main regions,
viz. the internal and marginal ligaments (Fig. 1), They are Yonge's (1977)
primary and secondary (periostracal) ligaments, respectively.
The glossy dark brown, amphidetic, marginal ligament unites the dorsal mar- gins of the valves. The supposed position of the pivotal axis may extend along
this marginal ligament. The location, appearance and funetion of the marginal
ligament of Plaeorna ephipptzem, P, lincolnii, and P. Iobata are very similar to
the outer layer of Pecten ma-xi･mzas (Linnaeus, 1758) illustrated by Trueman
(1953). Both anterior and posterior parts of the marginal ligament of Placuna.
A mt
me
.pll ,'･,･/'･i,-･,..,'･,･--
Fig. 1. Hinge region of the left valve of Placuna (Placuna) placenta (A) and Placuna (EphiPPium) ePhiPPium -e '.i '? (B). ti h'((A), a li.T (B)Oewas. ail: anterior inner ligarnent IUsuSagurT}t/rJwr, ml: mar- ginal Iigamznt wa enSew･'nt", pil :posterior inner ligament fisusewewenwt
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234 VENUS: Vol. 45, No.4(1987)
``teeth" plaeenta has small, periostraeal of Hornell (1909), which are distantly
spaeed and fall beakwards (Fig. IA). 'the The relatively large and thick, internal ligament is attached to valves in
Iigamental pits of the left valve and tooth-like ridges (nymphs) of the right
valve. Both anterior and posterior extremities of the ligament are long and 'two narrow and semicylindrieal. The internal ligament may be divided inte
parts, outer and inner layers (Fig. 2C). [Vhe thin, glossy dark brown to yel-
lowish brown outer layer is apparently homogeneous, laeks any struetural pattern,
and is curved outwards covering the thicker inner layer. The outer layer is
possibly referable to the lamellar layer of Newell (1938), The lamellar layer is
eomposed of protein hardened by aromatic tanning, giving molecular eross linkage
of adjacent polypeptid chains (Andersen, 1967), and is elastic under both ten-
sienal and eompressional stresses. The thiek, lustrous, yellowish brown, inner
layer shows fine growth lines and a fibrous texture. This is the fibrous layer
of Newell (1938). The inner fibrous layer is elastie under compressional stress
A c alp LV plp
-t /i" .; pftttpll alltttafl
acr taRV pcr
la--e...-J'''..'''1'y.l --.
acr RV ',r Fig. 2. Ligumenta･1 area of Ptacuna (EPhiPPiun-t) ephiPpium, P i F' i)' d O ew reo A, B :,location of cross section maveirin' (C) P)fiZW, C:cross sectl,on of ligarnental area ua"rtimaMgi im, D : lateral view of anterior crur21 ridge en 4']treMMU wh, acr : anterier crural ridge fu/u"va ee, afl : fibreus layer of anterior inner ligament ptilM;ew･"ff'fifJwr a) wakE ejdimpvasul all: lamellar layer of anterier inner ligament FtlsuStwurF/trMONt)( apfiiMS, alp:anterior ligamental pit eU/'IEmaxx, 1: inner ligarnent [N'MSmpW, la: location of ligamental attachment mpmeN'tsMS, LV:left valve Eif, pcr:posterior crural ridge thtivava, pfl: fibrous layer of posterier inner ligament iNMSew･'rt'iacvaa)wamettew ue-I, p]1: lamellar layer of posterior inner ligament Nutmpeec wta)Ealtas･'fi'rr' zz, plp : posterior ligamental pit ftEZtftrr", RV : r;Lght valve aue
NII-Electronic Library Service The malacologicalsocietymalacological society of Japan
Matsukuma: Family Placunidae (Bivalvia) 235
'the but not tensional one. A set of the lamellar and fibrous layers of internal
ligament forms a shallow C-spring or semicylinder. The internal ligament is
chiefly respollsibile fer the opening thrust en the valves.
The C-spring internal ligament of Ptacuna is structurally and functionally
identical with the parivincular ligament of heterodont bivalves (Trueman, 1949).
The term parivincular was proposed by Dall (1895) to describe the forrn ef
the ligament in Tellina, Cardium, Psammobia, and other speeies. The parivineular 'L'he ligament is cylindrical in shape, usually opisthodetie and is placed outside ef
dorsal margin. Trueman (1969) thought that it has probably evolved from an
opisthodetic ligament situated between the valve margins, as in Mytilzt･s or .Pinna
of the Pteriomorphia. The Pteriomorphia includes several varieties of the type of
ligament, e.g, alivincular ligament in Limopsidae, Vulsellidae, Limidae and Ost-
reidae, duplivincular in Arcidae, Cucullaeidae and Glycymerididae, multivincular
in Isognomonidae and transverse ligament between the valve margins in Mytilidae
and Pinnidae (Trueman, 1969; Waller, 1978). The internal, amphidetic C-spring
ligament with a dorsal lamellar (periostracab ligament in Placuna is unique and
is not known in any species of the Pteriomorphia. Anomia ephippium Linnaeus,
1758 has an elliptieal ligament on the crural stalk and laeks a marginal peri-
estraeal ligament, According to Yonge (1977) Placttanem･ia c･umingii Broderip,
1832, tropical eastern Pacifie species of the Plaeunidae, has a reversed V-shaped
ligament with outer lamellar and inner fibrous layers and lacks a marginal
periostracal ligament. Although a quantitative examination is highly required,
the structure and size of the ligament suggest that Placu･na species have the
most functional ligament among the Anemiacea. The Placuna C-spring ligament
and heterodont parivincular ligament may be a struetural convergence.
Family PLACUNIDAE Gray, 1842
Genus Plaettzaa rLightfoot, 1786]
1786 Ptacuna. [Lightfoot], 16. Type naeus, 1758. 1788 Placenta Philipsson in Retzius, 15. Type and translueent. Outer surface ornamented with fine radial threads. Hinge lacking a tooth, but having reversed V-shaped nymphs en the right valve only, 'twe Ligament censists of a conneetive lamellar layer at the dorsal rnargin and semicylindrieal parivineular-like ligaments on the nymphs and ligamental pits. Shell structure foliated calcite. Small, orbieular, posterior adductor scar placed at the center of the shell. Inner ventral margin smoeth. Etymotogy: Plaeuna, Latinized from the Greek nAate, anything fiat and broad. Subgenus Placuna (s.s.) NII-Electronic Library Service The malacologicalsocietymalacological society of Japan 236 VENUS: VoL 45, No.4(1987) Diagnos･is; Shell subcircular, flat and thin. Nymphs in the right valve diverging from each other; posterier limb longer than the anterior.gradual]y Plaonna (jPlae"na) ptacenta (Linnaeus, 1758) =r F' t)'-I (PL 1, figs. 1-2; Fig. IA) 1758 Anomia plaeenta Liiinaeus, 703 ["In Pelago"]. 1785 Anomia placenta Linnaeus: Chemnitz, 116, pl.79, f.716. 1788 Place7tta orbicularis Philipssen in Retzius, 15 [Indian Oceun]. 1792 [Placuw.a T)laee7't.ta b]: Bruguibre, pl.173, f,3. 1798 Ephippiu･m to'a7tsparens [R6ding, 166] [fig. of ref.: Chemnitz, 8 pl. 79, fig, 716; China; Tranquebar, India]. 1819 Pla.cutta placenta･ (Linnaeus) : Lamarck, 224 [Indian Ocean]. 1823 Anomia placenta Linnaeus: Mawe, 68, pl.15, fig.1 [Tranquebar, India; China]. 1826 PIactena ovaZis BlainviIle, 197 [no locality] (fide Iredale, 1939). 1855 Anomia placenta. Linnaeus: Hanley, 135. 1871 PXacuna placenta･ (Linnaeus): Sowerby, Plae'uo?.a sp. 3, pl.1, fig.3 [China; Phil- ippines; northwest Australia]. 1909 Placuna･ ptacenta 1932 Placu.tta ptacenta [Linnaeus): Kuroda, 122, fig. 123 [Japan; Taiwan]. 1939 Placzana placenta (Linnaeus) : Iredale, 408 [northern Queensland]. 1941 Placuna placenta 1959 Pla.cuna lincolnii Gray: Osama & Takemura, Plac'ttna pl., figs. 2-4, 9 [Philip- pines], 1966 Placu.na placenta (Linnaeus): Habe & Kosuge, 136, pl. 51, figs. 5-6, 1977 Placuna placenta (Linnaeus); Yonge, 502-514 [Singapore]. Material Exami.ned: Kawarnura Colleetion: Kaehsiung (NSMT-Mo 63894), Tai- wan (NSMT-Mo 63895): Philippines (NSMT-Mo 64008); locality unknown (NSMT-Mo 64009). Other sourees: Malaya (NSMT-Mo 63893); loeality un- known (NSMT-Mo 63899). Descri･ption: Shell moderately large, attaining 110 mm in length, suborbicular, bilaterally strongly eompressed, thin, translueent, subequilateral and slightly inequivalve. The lower right valve nearly flat and the upper left valve weakly inflated. Outer surface nearly smooth, excepting fine, radial threads and very weak, concentric laminae with minute frilles. Outer eolorations silver white, oecasionally with pale brown radial rays umbonally. Inner coloration glossy white. Nymphs ill the right valve rather weak and gradually diverging from each other; posterior ridge longer than the anterior. Posterior adductor sear NII-Electronic Library Service The malacologicalsocietymalacological society ofJapanof Japan Matsukuma: Family Placunidae (Bivalvia) 237 small, orbicular and placed at the center of the shelL Distrthution: Taiwan; Philippines; Hainan Island, seuthern coast of China; Borneo; Malay Peninsula; Indonesia; Queensland; India; Gulf of Aden. Subgenus Ephippium r'R6ding, 1798] 1798 Ephippizt,7z [R6ding], 166. Type (SD, Dall, 1898): Ephippium polo7zicu7n [Rtiding] [･-Placenta ephippittm Philipsson, 1788], 1807 Sellaria Link, 158, Type Diagnosis: Shell suborbicular or saddle-shaped and somewhat thiek. Nyrnphs in the right valve rapidly diverging from one another; anterior and posterior ridges nearly equal in length. Etymology: Latin, ephippium, i,, n., saddle, A 't Fig .3.Placuna (EphiPPi"m) ophiPPium (Philipsson, 1788), Pi i･'hd. NSMT-Mo63898, A-C: locality unknown, L 140mm, hypotype of Habe & Kesuge Cl966: 136, pl. 51, fig. 3). ,IA: outer viewofthe left valve EtufiSts, B: inner view of the left valve Encnwh, C: inner view of the right'IInner valve t-ituiJSdiil. D: NSMT Mo63897, Philippines, L 170mm, view of the left valve .6'.rvFgrfii). NII-Electronic Library Service The malacologicalsocietymalacological society of Japan 238 VENUS: Vol. 45, No. 4 (1987) Plcu7tna (]E))himpium) qphippium (Philipsson, 1788) a 7? F" hY (Figs. IB, 2-3) 1785 Ephippium angulicum max･imum...: Chemnitz, 111-114, pl.79, f.714. 1788 Placenta gzaadrangztla Philipsson in Retzius, 16 [Transquebar, India]. 1788 Place"ta ephippium Philipsson in Retzius, 16 [Indian Ocean]. 1791 Ano?nia sella Gmelin, 3345 [Indian Ocean]. 1792 [Ptacuna setla, P. papyracea]: Bruguibre, pl.174, f. 1-4. 1798 Eph･ippittm polonieum [R6ding], 166 [fig, of ref.: Chemnitz, 8, pl,79, f,714, Moluceas]. 1819 Ptaeuna sella (Gmelin) : Lamarck, 224 [Indian Oeean]. 1819 Placuna papuracea･ Lamarek, 224 [Indian Oeean]. 1871 Plaeuna sella (Gmelin): Sowerby, Placuna sp. 1, pl.1, fig. 1 [Indian und Chi- nese coasts], 1909 Ptacuna papuw'acea Lamarek: Lynge, 12 (108) [Thailand], 1909 Plaeuna Other sourees: Locality unknown (NSMT-Mo 63898). Description: Shell very large, attaining 210mm in length, subquadrately saddle-shaped, bi]aterally cempressed, more or less thick, subequilateral and inequivalve. Dorsal margin ]ong and nearly straight. Outer surface nearly smooth, exeepting fine radial threads. Outer coloration dark purpulish brown with white radial rays on the whole shell. Inner eo]oration glossy purple. Nymphs in the right valve nearly equal in length and widely diverging from each other. Posterior adductor scar small, suborbicular and placed at the center of the shell. Distribution: Taiwan; Philippi'nes; Ceram Sea, Indonesia; Queensland. Remarles: Kanno et al. (1982) recorded Placuna ephipptum from the upper Miocene Taranto Formation of central Luzon, the Philippines, NII-Electronic Library Service The malacological society of Japan Matsukuma: Family Placunidae (Bivalvia) 239 ]PZacztna (llphippium) tinootnii (Gray, 1849) lf 1 i 1 y b" rb'i (Pl. 1, figs. 3-4) 1849 Placenta "ncolnii Gray, 114, Moll. pl.1, fig, 1 [Australia]. 1871 Plaeuna lincoln･ii (Gray): Sowerby, Plaettna sp, 5, pL 5, fig. 5 [Australia], 1959 Placuna loba･ta (Sowerby): Oyama & Takemura, Placuna･ pl., fig. 7, 11 [Ara- fura Sea]. 1966 PlactLna quadriangMlar!'s (sic) (Retzius): Habe & Kosuge, 136, p),51, fig. 4 [northern Australia]. Materia･e Examined: Other sourees: Thursday Island (Horikoshi private coll,), Arafura Sea (NSMT-Mo 48580). Description: Shell moderately large, attaining 120 mm in length, subquadrate, bilaterally compressed, thin, subequilateral and inequivalve. Dorsal margin long and substraight, Outer surface nearly smooth, excepting fine radial threads. Outer coloration white with brown radial rays umbonally. Inner coloration grossy white. Nymphs in the right valve nearly equal in length and widely diverging from eaeh other. Posterior adduc:tor sear subeircular and plaeed at the eenter of the shell. Distribution: Arafura Sea, ]PZa(runa (thhimpium) tohata Sowerby, 1871 B V ab' V'? b' h'i ('re1'11i) (Pl. 1, figs. 5-8) 1871 Placuna･ lobata Sowerby, Placuna sp. 4, pl.4, fig. 4, pl.5, fig. 4b [Port Essing- ton (possibly Cobourg Peninsula, Northern Territory, Australia)j. 1879 Placenta planicostata Dunker, 214-215, pL 9, fig. 2 [no locality]. 1939 Placttna lobata Sowerby; Iredale, 408 [Queensland]. Material Examined: Other seurce: Palau, 10 fathoms (Horikoshi private col- lection, ex Wada, Seiji leg.). DescTiption: Shell subquadrate, subequilateral and inequivalve. The lower right Fig. 4. 0uter surface of Ptacuna (EPhiPPium) lobata showing lobed margin with diverging or converging radial threads, S V h' V7 I･' h t O ftwhxan NII-Electronic Library Service The malaoologioalmalacological societysooiety of Japan 240 VENUS ： Vo1 ．45， No ．4 （1987 ） valve nearly flat or slightly concave and the upper left valve weakly infiated． Ou 七er coloration pale brown with reddish brown rays and spots ． Outer surfaee ornamented wi 七h very slightly elevated ， broad， rounded ribs ．Ventral and dorsal margins roughly lobed with diverging or converging radial threads ． Inner colo − ration glossy white ． Posterior limb of nymphs of the righ 七 valve slightly 夏onger than the anterior ene ． Both Iimbs moderately widely diverging from each other ． − Distri・btttion： Palau ； Por 七 Essington （七ype locality）； Queensland （lredale， 1939 ）． 要 約 日 本貝類 学 会 名 誉会 長黒 田 徳米 先生 の 満 百歳 の 誕 生 目 を 祝 い ，先 生 が 1932年 に 概 述 さ れ た マ ド ガ イ 類 に つ い て ，靱 帯 の 構造 と 機・能 を 考察 し ，現 牛 種 の 分 類 を 再 検 討 し た 。マ ド ガ イ 科 は 殻 頂 部 に 痕跡 的 な足 糸開 口 を 持 ち ，泥 底上 に 転が っ て す む ，薄 い 円盤 或 い は 鞍 形 の 特 異 な 二 枚 貝 で あ る 。化 石 は 東 大 西洋 ， イ ン ド 洋 か ら知 ら れ て い る が ，現 生 種 は イ ン ド 四 太 平洋 の 熱 帯 域 に 限 ら れ て い る 。 ． マ ド カ の は に ’て つ の marginal ligament イ 科 靱帯 背縁 沿 ；， 分 布 し ，両 殻 を な ぐ役 割 縁 部靱帯 （ ） と， へ ligament 殻 内部 「Ai 形 に 突 き 出 し た 内 部靱 帯 （inner ） と か ら な る 。 内部靱 帯 は 右 殻 で は 歯状 に ． ． 突 き だ し た 着帯梁 に 乗 り ，左 殻 で は 着帯窩 に 納 ま る 。 内部靱帯 の 断 面 は 半 円筒 形 を 呈 し ，内側 に 繊 維 こ マ ル ス ダ レ 状靱 帯 部 が あ り，それ を 包 み 込 む よ うに 外 側 に 層状靱 帯 が あ る 。 の 構造 は ガ イ 超 科 の 二 ・ − 枚 貝 の 靱帯 （parivincular ligament ） に 類 似 し て お り， マ ドガ イ 科 に お い て も C spring の 1−E縮 ，反 発 を 利 用 し た 開 殻 機 構 が 採 ら れ （ い る こ と が 考 え ら れ る 。 一 ・ F ガ イ 科 は ， 軛 円 形 ，平 坦 な 殻 を持 ち ，小 さ い 角 度 で 交 叉す る 着 帯梁 を 備 え た マ ド ガ イ 属 （マ ド ． ガ イ 亜 属 ） Placuna （s ． s ，） と ，亜 円 角 形 或 い は 鞍 形 の 殻 を 持 ち ，大 き な 角度 で 交 叉 す る 着 帯 梁 を 備 え ク マ l た （ ラ ド ガ イ 亜 属 ）Piacuna （EPhippium ） に 瑁！れ 、る 。 − ’ Placuna （Placuna ） Placenta （Linnaeus ，1758） マ ド ガ イ 類 円 形 ， ド坦 ，銀 rl色，淡褐 色 の 放 射 ー 彩 条 を 持 つ も の も あ る 。台 湾 ，東 南 ア ジ ア ，北 東 オ ス ト ラ リ ア ，イ ン ド ， ア デ ン 湾 。 PtaCuna EPhippium ePhippium Philipsson ク ラ マ ド ガ （ ） （ ， 1788） イ 殻 は 厚 く， 鞍 形 。 自色 か ら ． 々 つ ース 黒褐 色 ま で 様 ，褐 色 の 放射 彩 条 を 持 もの もあ る 。 台湾 ，東南 ア ジ ア ，北東 オ ト ラ リ ア 。 シ ノ ノ メ マ Placuna （EPhippium ） lincotnii（Gray ，1849 ） ド ガ イ 並 四 角 形，や や 乎 坦 。 白色 で 褐 つ フ ラ 色 の 放 射 彩 条を持 。 ア ラ 海 。 Placuna （Ephippium ）lobata Sowerby ，1871 タ ソ ガ レ マ ド ガ イ （新称 ） 亜 四 角 形 ， 平坦 。淡 褐 色，赤 褐 色 の 放射彩 条 及 び 斑 点 が あ る 。腹縁 に は 大き な 褶 が あ り ，殻 表 に は 収斂 ，拡 散 を く り返 す 細 い 放 射 条 線が 走 る 。パ ラ オ ，北 オ ー X ト ラ リ ア 。 References Andersen ， S．0 ．1967 。 Isolation of a new type of cross link from the hinge hgament of molluscs α ture ： 1029 −1030 protein ．N ， 216 ． Bernard F R 1983 Catalogue of the living Bivalvia of the eastern Pacifie ： ， ． ． ． Ocean ｛orn α 冗 α め α t ： 1−132 Bering Strait to Cape I ．C d．Spec ．Pz 1．Fish ．Agu ．Sci．， （61 ＞ ． Blainville， H ． M 。 D ． de 1826 ． Vers 就 Zoophytes ． In ： Dictionaries des sciences natu − relles organise Vo1 41 2 fide Iredale 1939 ．Regne ． ． ， pt ． （ ， ）． Brugui6re ， Lamarck P A − ， J，G ， ，J．B ． ． ．de and Vincent，Bory de St，1791 1827．Tableau ・ encUcloPedi ． et ↑nethod tTois 「egnes α n α ture viii 180 488 que ique des de Z ． 十 p ．， pls．， Paris ， 一 NII-ElectronicN 工 工 Eleotronio Library Service The malacologicalsocietymalacological society of Japan Matsukuma: Family Placunidae (Bivalvia) 241 Broderip, W.J. 1832. Characters of new species of Mollusea and Conchifera. eollected by Mr. Cuming. Prec. Comm. Sci. Zool. Soc. Lo7tdon (16) : 25-33, Chemnitz, J. H. 1785. Neues systemat･isches Conchutien Cabinet, 8: 1-372, pls. 70-102, Nurnberg. Dall, W.H. 1895, 1898. Contributions to the Tertiary fauna of Florida, with special referenee to the Mioeene S･ilex beds of Tampa and the Pliocene beds of Caloosa- hatchie River. Parts 3, 4. Trans. Wagner IF'ree lnst. Sci., 3(3): 485-570 (1895); 3(4): 571-947, pls.23-35 (1898). Dunker, W. 1879, Mollusca quaedam nova. Jo"r de Conchyl., 27; 212-217, pl.9. Gmelin, J.F. 1791. Carol{ a･ Linne, Systeona･ na･turae, ed. 13. 1(6): 3021-3910. Lipsiae. Gray, J. E. 1842. Sy7zopsis o.f the contents o.f the British Mugeum, ed. 44. iv+308p., British Mus., London Gray. J. E. 1849. 0n the species of the genus Placenta･ of Retzius. Proc. Zool. Soe. Lendon, for 1849: 114-115, Moll, pl.1. Habe, T. 1953. Pinnidae, Plaeunidae and Anomiidae in Japan. Ill. Cat. Japan. Shells, 1<24): 185-200, pls. 24-28. Habe, T. and Kosuge, S. 1966. Shells o.f the world in eetour. 2, 194 p., 68 pls., Hoiku- sha, Osaka. Hanley, S. 1855. Ipsa Li,nnaei conchylia, 556p., 5pls., London. Hatai, K. 1941, Recent marine shells of the South Sea Islands. Butt. Trop. Indt{st. Inst. Palazt S. Sea Js. Japa7t, (7): 1-160, pls. 1-79, Hornell, J. 1909. Report on the anatomy of Ptacuna ptacenta, with notes upon its distribution and economie uses. Rep. Mar. Zool. Okhamandal, 1: 43-97 Iredale, T. 1939. Mollusea. Sci. Rep. Great Barrier Reef Exp. 1928-29, 5(6): 209- 425, pls. 1-7. Janssen, R. 1979. Revision der Bivalvia des Oberoligozans. GeoL Abh. Hessen, 78: 1-181, pls. 1-4, Kanno, S., O'Hara, S. and Caagusan, L, 1982. Molluscan fauna from the Tartaro Formation (upper Miocene) of eentral Luzen, Philippines. Geol. Pqlaeont. SE Asia, 24: 51-128, pls.14-19. Keen, M. 1959. Some type designations in AnQmiacea. Min. Cench. Club S, Calif., <191): 22. Kuroda, T. 1932. An illustrated catalogue of the Japanese shells, Vent{s, 3(4): app, 113-122. Kuroda, T. 1941, A catalogue of molluscan shells trom Taiwan Lamarek, J.B,P.A. de Monet de 1801. Systems des animaux saits vertebres. viii+ 432p., Paris. Lamarek, J. B. P. A. de Monet de 1819. Histo･ire naturelle des aniona-ux sans vertebres. Vol. 6, pL 1, pp. 1-343. [Lightfoot, J.] 1786, A catalogue of the Portland Museuon, etc. viii+194p., London, NII-Electronic Library Service The malacological society of Japan 242 VENUS: Vol.45, No.4(1987) Link, H.E 1806-1808. Beschreibung der Natztralien-Sammlung der Universitat zu Rostoek. 160p. 30+38+38pls,, Rostock. Linnaeus, C. 1758. Systeona naturae, ed. 10. Vol. 1, Regnum animale, pp. 1-824. Lynge, H. 1909, The Danish expedition to Siam 1899-1900. IV. Marine Lamelli- branchiata. D. Kgl. Vidensle. Setsic. Slerifter nat. og. math., [7] 5(3>: 97-299, pls. 1-5. Mawe, J. 1823. The Mnnean system o.f conchology, 207p., 37pls., London, Newell, N.D. 1938. Late Paleozoic peleeypods: Peetinacea, Publ. Kansas State Geol, ' Surv., 10<1): 1-123. Olsson, A.A. 1961. Mollusks of the tropieal eastern Pacific, particularly from the southern half of the Panamic-Pctci.Ec faunal province (Pana7na to Peru). 574p., 86pls., Paleont. Res. Inst., Ithaea, Oostingh, C. H, 1925, Repert on a coltection of Recent shetls from Obi a.nd Halmahera ' (Moluecas), 363p., H. Veenman & Zonen, Wageningen, Holland. Oyama, K. and Takemura, Y. 1959. The mollusca･n shells (3). 30 pls,, Sei. & Photo Club, Tokyo. Philippson, L.M. 1788. See Retzius, 1788. Retzius, A.J. 1788. Dissertatio historico-na･turalis sisteizs neva testaceoru7n ge7tera. 23 p., Lund. [R6ding, P.F.] 1798. Museum Boltenianum. Pt. 2, 199p., Hamburg. Schmidt, F. C. 1818, Versuch uber die beste Einrichtung xur Aufstell?mg, Behaflcltung tcnd Aufbewahning der versiedene" NaturkoTper u"d Gegenstande der Kunst, vo･r2uglich der Conchylien-Sammlungen,,..252p. (fide Simpson, 1900, Proc. U.S. Nat. Mus. 22(1205)). Sowerby, G.B. (III) 1871. Monograph of the genus Ptaeuna, Conch, Ieon., 18: Pla- ' cu7ta spp. 1-5, pls. 1-5. Stoliczka, F, 1871. Cretaeeous fauna of southern India. The Pelecypodaf with a re- view of all known genera of this class, fossil and Reeent. Palaeont. Indica, [6]3 (9-13): 409-537, pls. 29-50. Taylor, J. D., Kennedy, W,J. and Hall, A. 1969. The shell strueture and mineralogy of the Bivalvia. Introduction, Nuclacea-Trigonacea. Bull. Brit, Mus. (Nat. Hist.), [Zool.], suppl., 3: 1-125, pls. 1-29. Trueman, E.R. 1949. The ligament of Tettina tenuis. Proc. Zool. Soc. London, 119 (3): 717-742. Trueman, E.R. 1953. 0bservations on certain mechanieal properties of the ligament of Pecten. Jour. Exp. Biot., 30(4): 453-467. Trueman, E.R. 1969. Ligament. In; Moore, R.C. (ed.): Treat. Invert. Pal., pt. N, MolL 6, voL 1 of 3, pp. N58-64. Waller, T. R. 1978. Morphology, morphoelines and a new classifieation of the Pterio- morphia (Mollusca: Bivalvia). Phil. Trans. Roy. Soc. London, [B], 284 (1001): 345-365. Watson, H. 1930. 0n the anatomy and aMnities of Pticatula. Proc. Malac. Soc. Lon- don, 19: 25-31, pl. 5, Yokoyama, M. 1928. MQIIusca from the oil-field Qf the Island Qf Taiwan. Rep. Imp. NII-Electronic Library Service The malaoologioalmalacological societysooiety of Japan Matsukuma ： Family Placunidae （Bivalvia） 243 ＿＿ − Geel． Surv ． Jap αn ， （101 ） 1 112， pls．1 18 ． − Yonge ， C ． M ．1977． Form and evolution in the Anomiacea （Mo11usca ： Bivalvia） ∠ α ： α cun α nomi α α cun 配 PododesmttS ， 4nemi ，Patro，Enigmonia （Anomiidae ） Pl ， Pl B 276 950 ： 453 −523 （Placunidae，Fam ．Nov ．）．Phil．Trans ．Roy ．Soc．London ， ［ ］， （ ） ． Plate 1 （overleaf ） − マ ド ガ イ 1 ， 2． Placzana（Placuna ）placenta（Linnaeus ，1758 ） 。NSMT Mo 63895 ，Taiwan ， L60mm ．〔1 ： 0uter view of the leftvalve 左殻 外 面 ， 2 ： innerview of the right valve 右 殻 内面〕， 3 シ ノ ノ メ マ −Mo ，4． Ptacuna （Ephippium） tincolnii（Gray ， 1849） ドガ イ 。 NSMT 48550 Arafura Sea ， L 115mm ．〔3 ： 0uter View of the left valve 左殻 外 i l， 4 ： inner view of the right valve 右殻 内 面 〕， − ー 5 8． Placuna （Ephip ρium ）lobata Sowerby ，1871 タ ソ ガ レ 1 ド ガ イ （新 称）。 Horikoshi private collection ， Palau ， L 45mm ．1：5 ： 0uter view of the right valve 右殻 外 面 ， 6 ： inner view of the left valve 左殻 内面 ，7 ： degenerated byssal foramen near umbo of the right valve ： 右 殻殻頂 部 の 足 糸 開 ロ の 痕 跡 ， 8 surface ornamentation of the left valve 左殻 の 表面 装飾〕． 一 NII-ElectronicN 工 工 Eleotronio Library Service TheThemalacologicalsociety malacological society of Japan 244 VENUS: Vol. 45. No.4 (1987) Plate 1 NII-Electronic Library Service