17 113 
he refers Arca lactea var. erythraea, Issel, from the Red Sea to A. decussata, Reeve 
(Sow.), as stated by A. H. Cooke,’ it is in reality only a form of A. lactea L. — 
Lamy in his latest revision of the gen. Arca” regards A. complanata, Ch., somewhat 
differently from the way in which I regard it here. He gives A. velata, Sow., as a 
variety of A. complanata, Ch. (which he names A. nivea, Ch.), and places A. decussata 
as a distinct species; but as Lamy’s work was not published until I had finished 
my work upon the Arca-group, I have not been able to consider it here. 
Arca (Barbatia) lima, Reeve. 
Arca lima, Reeve, Proc. Zool. Soc. Lond., XII, 1844, p. 125. 
—- — Ss Conchol. icon., IH, Sp. 101. 
—  (Barbatia) lima, Reeve, Martini u. CakMN., Conchyl. Cabin., VIII, 2 Abth., p.115, pl. 30, figs. 5—6. 
- Epg. A. Smirn, Lamellibranchiata of the Challenger Exped., p. 260. 
= Report on the zoolog. collect. made during the voyage of 
H.M.S. “Alert,” p. 110. 
E. Lamy, Bull. du Mus. d’Hist. Nat. Paris, 1904, p. 273. 
— decussala, Sowensy var. lima, REEVE, LaMy, Journ. de Conchyl., vol. 55, 1907, p. 65. 
Koh Kram, 6—10 and 30 fathoms (3). E. of Koh Chuen, 9—10 fathoms, shells (2). 
Koh Chuen, 10—15 fathoms (2). S. of Koh Chuen, 30 fathoms, shells (*/2). Off 
Koh Kam, 10 fathoms, gravel (1). Gulf of Rayong, sand, mud and _ shells (1). 
North and west coast of Koh Chang, 1 fathom, old coral blocks (12). Koh Kahdat, 
1 fathom, sand (2). W. of Koh Kut, 30 fathoms, sand and mud (?/2). Between Koh 
Kut and Koh Kahdat, 10 fathoms, shells (5). S. of Koh Kahdat, 8—10 fathoms, mud (*/2). 
Long. 3—45 mm. 
Distribution: — Singapore (low water, Sv. Gap), Madras, Gulf of Manaar, 
Laccadive and Maldive Archipel., Gulf of Aden, Red Sea (pleistocene). — Philip- 
pines, Torres Str., Port Molle, St. Vincent’s Gulf, South Australia, South. Paumotu Isls. 
The following species may safely be reckoned as synonymous with Arca lima, 
Reeve: — Barbatia oblonga, Dkr.* (non Anomalocardia oblonga, Phil. et Dkr.), Arca 
granulala, Phil.,* from the Sandwich Islands, Barbatia (Acar) acera, Mely. & Stand.° 
Ena. A. Smiin® states that A. trapezina, Lam. (“as determined by REEVE”), is probably 
a form of A. lima, Reeve; how far trapezina, Lam., is on the whole a form 
of A. lima I am not at present prepared to say; that the whole Barbatia-group 
when, later, a larger quantity of material is at hand and further comparalive in- 
vestigations have been carried out — will unquestionably be reduced in many 
respects, is practicaliy certain. In many cases it is very difficult to determine young 
specimens of A. lima and to keep them distinct, as for example from A. complanata, 
' Annals and Magazine of Nat. Hist., 5. ser., vol. 18, 1886, p. 93. 
* Journ. de Conchyliologie, vol. 55, 1907, p. 59. 
* Novitates Conchologicae, p. 107 and p. 85. 
* Abbild. und Beschreib. neuer od. wenig gekannt. Conchyl., Ill, p. 114 (22), pl. VI, fig. 3. 
* Journ. Linn. Soc. Zoology, vol. XXVII, p. 186, pl. 10, fig. 15. 
® Proc. Zool. Soc. London, 1891, p. 431. : 
D, K. D. Vidensk. Selsk. Skr., 7. Reekke, naturvidensk, og mathem. Afd. V. 3. 15 
