116 20 
separated from the two other forms mentioned above, at any rate as far as the 
specimens from the Gulf of Siam are concerned. These agree entirely with the 
diagnosis and figure by Reeve, and also with the excellent description by EpGar 
Sirn of A. sculptilis. They do not at all resemble the figure of Lamarck’s original 
specimen of A. pisolina (in Journal de Conchyl., vol. 52, 1904, pl. 5, figs. 6—7); neither 
do they agree with ReEve’s diagnosis and figure of his species A. solida. The great 
number of specimens which I have before me all show a white colour under the 
thin epidermis. A. Zebuensis, Reeve, is undoubtedly synonymous with A. sculptilis. 
Arca (Fossularca) tenebrica, Reeve. 
Arca tenebrica, Reeve, Proc. Zool. Soc. London, XII, 1844, p. 126. 
= — Conchol. icon., Il, Arca, Sp. 105. 
— (Barbatia) tenebrica, Reeve, Marrint u. Caoemnirz, Conchyl. Cabin., VU, 2 Abth., p. 156, pl. 39, 
figs. 7—8. 
= — — - Epc. A. Smira, Report on the zoolog. collect. made during the voyage 
of H. M.S. “Alert,” 1884, p. 110. 
(Fossularca) - Lamy, Journ. de Conchyl., vol. 55, 1907, p. 105. 
Coast of Lem Ngob (1). North end of Koh Chang, 1 fathom, old coral blocks (4). 
Koh Chang, between stones at very low tide (46). Gulf at the south end of Koh 
Chang (1). Strand of Koh Kahdat ('/2). 
Long. 7—16 mm. 
Distribution: — Bombay, Karachi (Metvitt & SranpEN). — Philippines; 
Japan (Nagasaki), Port Essington, Port Curtis. 
The epidermis is extremely velvet-like in several of the specimens from the 
Gulf of Siam, and the outline in this species varies rather considerably. 
Arca (Acar) plicata, Ch. 
Arca plicala, Cuemnirz, Conchyl. Cabin., XI, 1795, p. 244, pl. 204, fig. 2008. 
(Acar: plicata, Cuemnirz, Marvini u. Cuemnirz, Conchyl. Cabin., VIH, 2 Abth., p. 195, pl. 47, fig. 5. 
_ — — E. Lamy, Bull. du Mus. d’Hist. Nat. Paris, 1904, pp. 274—75. 
- - 7 - Journ. de Conchyl., vol. 55, 1907, p. 80. — Bull. du Mus. d’Hist. 
Nat. Paris, 1906, p. 317. 
squamosa, LAMAKck, Anim. sans vert., VI, part. 1, 1819, p.45, No. 35, — éd.2, VI, p. 474, No. 35. 
= — Savicxy, Descr. de Egypte. Mollusques, pl. 10, fig. 6. 
- -- Lamy, Journ. de Conchyl., vol. 52, 1904, p. 142. 
Barbatia squamosa, LAManck, Prircuann and Gariirr, Proceed. Roy. Soc. Victoria, vol. 17, part. 1, 1904, 
p. 241. 
Arca Domingensis, Anim. sans vert., VI, part. 1, 1819, p. 40, No. 16. — éd. 2, VI, p. 467, No. 16. 
- Liscukr, Japan. Meeres-Conchyl., Il, p. 142 u. HI, p. 107. 
— (Acar) domingensis, LAmMAnck, Ep. A. Smrru, Lamellibranchiata of the Challenger Exped., p. 265. 
— gradata, Bropvenip and Sowrrny, Zoolog. Journal, IV, 1829, p. 365. 
— - Gray, Zool. of Beechey’s Voyage, p. 152, pl. 43, fig. 1. 
— — = - — Han.ey, Rec. biv. shells, p. 155, pl. 18, fig. 39. 
~- Reeve, Conchol. icon., Il, Arca, Sp. 92. 
Byssoarca divaricata, Sowensy, Proc. Zool, Soc. London, I, 1833, p. 18. 
Arca Reeve, Conchol. icon. Il, Arca, Sp. 108. 
