CHAPTER V BIVALVIA CHAPTER V BIVALVIA INTRODUCTION This chapter deals with the marine bivalves, which are quite abundant when compared to the gastropods in the marine Quaternary ueposits of Raigad District, Maharashtra. The marine mollusc~, i.e. bivalves and gastropods of the ~est Coast of India were studied in the early days by Melvill and Abercrombe (1893) and Melvill and Standen (1901). And after a long gap of time that the marine pelecypods of Bombay Coasts were studied by Subrahmanyam, Karandikar and Murti (1949), describing several genera and species. From the Karwar Coast, Patil (1952, 1954) described the mollusca including both bivalvia and gastropods and gave an exhausting list. Similarly, from the Krusadai Island, Gulf of Manner, Palk Strait, Coromandal Coast the marine mollusca were studied by Chricton (1941) and Gravely (1942). Later in 1956, Satyamurthy described in detail, the bivalves from these places. SYSTEMATIC DESCRIPTION Phyllum Mollusca - r' Class Bivalvia Linn, 1758 (Buonanni, 1681) Subclass Palacotaxodonta Korobkov, 1954 Order Nuculoida Dall, 1889 - 64 - S u pe r-f ami 1 y Nuculanacea H Adams & A. Adams, 1858 Family Nucu lan id as Adam & Adam Genus Portlandia March 1857 Subgenus .£:. ( Po r t lan d i a ) March, 1857 £. ( Portlandia) Sp. indet (Pl. XI, Fig. 7) Material : Single broken specimen No. MACS G 2391 Measurements Length Height Thickness L/H L/Th No. MACS G 2391 2.0 em 0.9 em 0.4 em 2.2 5 De scription Shell thin, small, elongated and sub- triangular; umbone amphidetic, ligament thin; ventral margin straight, smooth, ante.rior margin broken, posterior margin gently rounded; ornamentation of faint concentric lines; hinge straight, taxodont; internal margin smooth, Pallial line not seen. Remarks .0 I Present specimen can be assigned to the genus Portlandia (Portlandia) March on the basis of outline and indistinct posterior furrow. (Cox~ 21. 1969, P.N 23 g, Fig. A 9, 4) the hinge character is similar to Yoldia aretica Gray but the posterior is truncate, (which is not so in the present case (Zittel, 1937, P. 441, Fig. 657). So in view of - 65 - insufficient material thespecmen is placed under the genus Portlandia. But better and more material may need change in generic position. Occurrence Limestone of Dive Agar Formation at ShekhadJ. • Sub-class Pteriomorpha Beurlen, 1944 Order Arcoida Stoliezka, 1871 Super-family Arcacea Lamarck, 1BD9 ~amily Arcidae Lamarck, 1809 Sub-family Arcinae Lamark, 1809 Genus Barbatia Gray, 1842 Sub-genus ~.(Barbatia) · Gray, 1842 ~· (Barbatia) bistrigata (Dunker) (Pl.X, Fig. 3) 1949 Area bistrigate Okr. Subrahmanyam et ~, p. 59, Fig. 9 1951 Dkr. Hornell & Tomlin, p. 90 Material Several specimens Plesiotype No. MACS G 2411 - 2413 Measurements Height Length Thickness L/H L/Th MACS G 2411 2.3 em 3.7 em. 1.1 em. 1.60 3.36 Description Shells thick, mediuw.-sized, elongate, equivalved, inaquilaterla; umbo prosogyrate, about l / 3rd from anterior, ligament duplivincular, amphidetic, cardinal - 66 - area low; margins round, ventral margin slightly protruding out; ornamentation of numerous fine radial ribs bifuncating concentric growth lines weak; hinge long, straight bearing small, numerous teeth, convergent terminally; internal margin smooth. Remarks The present material agrees with B. bistrigata (Dank.) from Penang in the collection of Z.S.I, having Reg. No. 4487. Occurrence Shell limestone of Dive Agar Formation at Kashid and Velas. Barbatia (Barbatia) sp. (Pl. X, Fig. 10,13) Material : No. MACS G 2414 - 2416 Measurements : Height Length Thickness L/H L/Th No. 2414 2.1 3.9 1.3 1.9 3 Description Shell thick, medium-sized, Quadrate, posterior obliquely truocated, ligament amphide tic, umbo prosogyrate; ornament on anterior half of closely-spaced biturcating ribs with narrow intervening spaces, posterior half with primary ribs divided into close-spaced size rib-lets, primary ribs separated by narrow, dee p intervening grooves, internal margin thick with short and long radial striations. - 67 - Remarks : Present specimen differs from Balbatia (Barbatia) bistrigata (Dunker) (Vide supra) and~ (B.) barbata (Linne) (Cox et 1!!..z. 1969, P.N 252, Fig. C2, 63; Dance, 1977 p. 224 with fig ) in having different ornament pattern on anterior and posterior sides. Area fusca Bruguiere and Area complanta Chemnitz (Satyamurthy, 1956, p. 21-22, Pl. II, Figs. 3 a-b, 4 a-b) are nothing but Barbatia fu~ca and ~· complanta. They also differ from the present specimen on ornamentation. Occurrence : Shell limestone of Dive Agar Formation at Akshi. Sub-family Anadarina Reinhart, 1935 Genus Anadara Gray, 1847 Sub-genus A. (Anadara) Gray, 1847 Anadara (Anadara) granosa (Lamarck (Pl. X, Fig. 8; Pl. XI, Fig. 14, 15) 1949 Area granosa Lam. : Subrahmanyam --et al, p. 59, Fig. 4 1951 Lamarck : Hornell & Tomlin, p. 90 1977 Anadara granosa (Linnaeus) : Dance, p. 224 Material Several specimens Plesiotype No. MACS G 2392 - 2394 Measurements Length Thickness Height L/H L/Th MACS G 2392 4.7 em 1.9 em 3.7 em 1.27 2.47 2393 3.7 em 1.6 em 3.1 em 1 .19 2.31 - 68 - Description : Shell thick , sub-trapezoidal., thick, equivalved, inequilateral, umbo prosogyrate, ligament amphidetic, cardinal area broad, triangular; ventral margin broadly rounded; surface sculpture of strong scabrows, radial ribs counting 19-23 in number, separated by smooth interspaces; hinge straight bearing uniform taxodont teeth; internal margins strongly crenulated, depressions corresponding to the raised ribs on the surface. Remarks : The present specimens agree well with Anadara (Anadara) granosa preserved in Z.S.I. museum No. Occurrence : Shell limestone of Dive Agar Formation at Akshi and Korlai. Genus Larkinca Reinhart Larkinia fhombea (Bar~) (Pl. X, Fig. 1, 2) 1949 Area rhombea Born Subrahmanyam et ~' p. 59 1951 .• Born Hornell & Tomlin, p. 90 Material Several specimens Plesiotype No. MACS G 2395- 2397 Measurements Length Height Thickness L/H L/Th MACS G 2395 5 o 7 em ~ 5 G2 em. 2 $8 em. l o09 2s03 em. 2396 2 e 1 em. 1.1 em. 1.23 2 o36 em. - 69 - Description Shell big, thick, stout, sub-trapezoidal, equivalves, inequivalateral; almost same in height and length; umbo elevated, prosogyrate, ligament amphidetic, broad, triangular; ventral margin broadly rounded; posterior margin truncated; sur§ace, sculpture of strong, radiating, scabrons ribs intervened by furrows, beaded on anterior side, posterior side truncated and ribs closely spaced; hinge slightly curved, dentation typically taxodont; internal margins crenulated corresponding to the elevated ribs on the surface. Remarks The present material agrees with Anadara rhombea in Z.S.I. museum from Andaman Islands bearing Reg. No. M. 3465/1 and M. 3421. Occurrence : Shell limestone of Dive Agar Formation at Velas and Aravi. Genus Scapharca Gray, 1847 Sub-Genus 2· (Scapharca), Gray, 1847 Scapharca (Scapharca) deyrollei Jousseaume (Pl. X, Fig. 11, 12) Material Plesiotype : No. M.ACS G 2398 -2400 - 70 - Measurements : Length Height Thickness L/H L/Th r~ACS G 2398 1 • 0 em. 0.7 em. 0. 4 em. 1.42 2.5 Description Shell relatively thin, slightly convex, equivalved, very inequilateral, trapezoidal; umbo proso- gyrate, ligament very narrow; margins round but. p o s t e r i o r ma r gin e x p an de d , sur f ace o r n amen t at ion t h a t o f numerous, fine radiating ribs; hinge straight, taxodont, teeth converging to a point below the beak; internal margins crenulated. Remarks : Present specimens compared with Scapharca (Scapharca) deyrollei preserved at z.s.r. museum are found to be identical with them. Occurrence Shell limestone of the Dive Agar rormation at Aravi. Scapharea (Scapharea) inaeguivalvis (Brunguiere) (Pl. X, Fig. 5, 6) 1941 : Area inaeguivalvis : Gravely, p. 32, Fig. 14 f. 1949 Area inaeguivalvis Brug : Subrahmanyam ll ..§!l, p. 59 Fig. 8 1951 Brug : Hornell & Tomlin, p. 90 1956 ~ inaeguivalvis Bruguiere : Satyamurthy, p. 24, Pl. II, Fig. 7 a,b. 1969 Scapharca (Scapharca) inaeguivalvis (Brug) Cox~~~ p. 256, Fig. C 5, 6 - 71 - Material : Several specimens. Plesiotype : No. MACS G 2401 2402 Measurements Length Height Thickness L/H L/Th MACS G 2401 4.7 em. 4.2cm. 2 .1 em. 1 • 11 2.23 2402 2. 8 em • 2. 5 em. 1.1 em. 1.12 2. 54 Description : Shell medium~sized, trapezoidal, equivalved, inequilateral, umbo prosogyrate, slightly flattened, ligament amphidetic, narrow, margins round, posterior than the anterior; ornamentation of strong, flattened radiating ribs with rectangular cross-section, hinge long, teeth padded j~st below the hinge, converging below umbo; internal margins creunlated. Remarks : Present material is compared with Scapharia (Scapharca) inaeguivalvis preserved at Z.S.I. museum and agrees with it. Occurrence : Shell limestone of Dive Agar Formation at Vel as and Aravi. Scapharca (Scapharca) gubernaculum (Reeve) (Pl. X, Fig, 9) 1956 Area gubernaculum Reeve Satyamurthy, p. 25, Pl. II, Fig. 8 a-b - 72 - Material : Several specimens Plesiotype No. MACS G 2403 - 2405 Me a su ramen t s Length Height Thickness L/H L/Th MACS G 2403 3 .1 em. 1 .8 em. O.S em. 1 • 72 3.44 2404 3.7 em. 2 • 1 em • 1 • 0 em. 1. 76 3.7 " G 2405 Description Shell moderate, trigonal, elongated, equivalved, inequi1ater61, umbo small, prosogyrate, ligament amphidetic, narrow, margins rounded, ventral margin broader; surface ornamentation of strong, flattened radiating ribs with rectangular cross-section; separated by flattened interspaces, hinge slightly arched, taxodont; internal margins crenulated corresponding to the ribs on surface. Remarks Present material ag~ees with Scapharca (Scapharca) gubernaculum from Penang, preserved at Z.S.I. museum bearing No. 4527. Occurrence Shell limestone of Dive Agar Formation exposed at Akshi, Dive Agar, Velas, and Boralai. Scaphar ca .2.£. (Pl. X, Fig. 4, 7) Material : Single specimen Plesiotype : No. MACS G 2406 - 73 - Measurements Length Height Thickness L/H L/Th MACS G 2406 4.