126 30 
Arca gubernaculum, Reeve, Martini u. CHemnirz, Conchy]. Cabin., VII, 2 Abth., p. 107, pl. 28, figs. 5—6. 
— — P. Fiscuer, Catal. d. Moll. de l’'Indo-Chine, p. 272. 
— (Anadara) gubernaculum, Rerve, Lamy, Journ. de Conchyl., vol. 55, 1907, p. 239. 
— chalcanthum, Rerve, Proc. Zool. Soc. London, XII, 1844, p. 44 (fide Epa. Smrru). 
= — _— Conchol. icon., Il, Arca, Sp. 43. 
— Luzonica, REEVE, Proc. Zool. Soc. London, XU, 1844, p. 44 (fide Epc. Smrrn). 
— — — Conchol. icon., Il, Area, S. 44. 
“Golfe de Siam,” L. Morter (P. Fiscuer loc. cit.). 
The Danish Expedition collected no specimens of this species in the Gulf 
of Siam. 
Distribution: — Philippines, China, Formosa, Port Jackson. 
Arca (Scapharca) indica, Gm. 
(Pl. II, Figs. 5-12). 
Arca indica, GMr.in, Syst. Nat., ed. XII, 1790, p. 3312, No. 27 (excel. var.). 
(— _ - Lamarck, Anim. sans vert., VI, p. 473, No. 31). 
(— — - Reeve, Conchol. icon., Il, Arca, Sp. 56). 
= — — Martini u. CHeMNitrz, Conchyl. Cabin., VIII, 2 Abth., p.11, pl. 2, fig. 2. 
— (Argina) indica, GMe.in, Lamy, Journ. de Conchyl., vol. 55, 1907, p. 295. 
— Indiae Orientalis, CHemnirz, Conchyl. Cabin., VII, 1784, p. 196, pl. 55, fig. 543. 
Ostindische Bastarlarche, Marrini, Beschaftig. d. Berlin. Gesellsch. Naturf. Freunde, III, 1777, pp. 288—90, 
pl. 6, fig. 13. 
Coast of Lem Ngob (*/2). : , 
Long. 21—44 mm., alt. 11—23 mm. 
Distribution:— Coromandel Coast (Tranquebar; CHemnirz). HANLEy'! records 
the species from Sumatra. In the Museum in Berlin are specimens from Sumatra; 
North-west Australia (MENKE). This species is probably more widely distributed. 
By comparison with original specimens of Arca indica, Gm., from Tranque- 
bar, from SpeNGLER’s collection in the Zoological Museum of the University of 
Copenhagen, I have been able to identify the specimens from the Gulf of Siam. 
The present species has hitherto been badly figured and described. Lamarck, 
REEVE and Koper,” all say, that the area is absent in the species; this is nol 
correct (GMELIN also does not mention it). Normally, there occurs an area which 
is rather narrow and striped* as shown in the figures, Pl. II, Figs. 9 and 12; it 
is, however, frequently reduced to a minimum, and as the yalves, thereby, have 
their umbones placed closely together, the latter become much worn; the hinge- 
teeth also suffering by this reduction of the area. The ribs, 30—386 in number, 
are flattened and broad. From the umbones downwards to the ventral margin the 
valves are frequently somewhat concaye in the middle. Rereve’s figure certainly 
1 Catalogue of recent bivalve shells, p. 158. As Haney in mentioning this species says: “with 
many ribs, which are grooved in the middle” it can hardly be the present species. 
* Martini & Cuemnirz, Conchyl. Cabin., loc. cit. 
5 Cuemnirz (loc. cit., Vil, p. 197) says: “Der kleine zwischen den Wirbeln befindliche, etwas ver- 
tiefte Raum wird von einen schwarzlichen lederartigen Bande bedecket,” 
