TRIBE ARCACEA. 153 
heart-shaped, white spotted internally with brown. +.—New 
Holland. 
A. Carpissa. Lam. 8.—Del. t. 11. f. 14. Nut-shaped and 
transversely heart-shaped, valves keeled on the back, beaks almost 
obsolete so as to cause the dorsal edge to seem quite flat; the 
ligamental area lozenge-shaped and flat; ventral margin convex 
and gaping. 2.—British Channel.—A small inequilateral shell 
of an extraordinary shape for this genus. Placed on the pointed 
extremity of its elongated side, it wears the semblance of Cardium 
Cardissa, but without any apparent beaks. 
A. Sutcata. Lam. 11. Ovate, very obtuse posteriorly, and 
obliquely truncated anteriorly, entire, gaping; white clouded with 
reddish brown, with longitudinal grooves which are transversely 
striated and subcrenated. 14.— New Holland. 
A. Ovata. Gi'mel. 3307.—Lam. 12.—W. t. 9. f. 12.—A. 
Nivea. D. p. 230.—Ch. f. 538.—E. t. 309. f. 3. Ovate, 
somewhat sinuated, ventricose, but depressed in the middle and 
rather angulated at one end, with crowded narrow decussated ribs 
under a scaly and brown epidermis, margin gaping in the middle, 
no posterior depression. 13..23.—Red Sea.—Deshayes holds 
this to be the same as Helbingii.2 
A. Barpara. Lin. 1140.—D. p. 229.—Lam. 13.—W. t. 9. 
Sf. 3.—Ch. f. 535.— Bl. t. 65. f. 1.—E. t. 309. f. 1. Trans- 
versely oblong, depressed, somewhat sinuated in the middle, 
reddish brown becoming paler centrally under a brown epidermis 
which forms shaggy bristles on the crowded raised longitudinal 
strize, (crossed by delicate transverse ones); margin nearly closed, 
the umbones depressed but the beaks not distant, and the area 
between them covered by a brown ligament which adheres to it by 
means of several grooves nearly parallel to the hinge.— Variety. 

1 A. Ventrricosa. Lam. 9. being but a variety of No# must 
be suppressed.— Deshayes. 
A. Retusa. Lam. 10.—Ch. f. 432. Oval, ventricose, obtuse 
at each end, decussated by the striz, the longitudinal grooves sub- 
imbricated: ligamental area brown and glabrous.— The specimens 
in the French Museum, being old Naviculares and the figure of 
Chemnitz being universally assigned to Imbricata, it is probable 
that this species must be expunged from our future catalogues. 
2 Of this species, Deshayes considers as a variety the A. TRa- 
PEZINA. Lam. 18.— Del. t. 11. f. 13. Ovate, elongated, subtra- 
peziform, depressed, pellucid, longitudinally grooved and transversely 
striated, the umbones smooth, the anterior edge very oblique and 
incurved, ventral arcuated ; area between the beaks concave and 
rather narrow. 14.—Timor and South Seas. 
