142 TESTACEOUS MOLLUSCA. 
truncated, flattish, and slightly keeled at its border, but becomes 
elevated towards the margin of the valves : within quite white. 13. 
1.—W. Indies. 
C. Fracum. Lin. 1123.—D. p. 118.—Lam. 41.—Ch ff. 
166, 7.—£. t. 295. f. 3.— Wood. G. C.i58: (23: War 
f. 51. Somewhat heart-shaped, angulated and truncated ante- 
riorly, yellowish white with about twenty-three rather depressed 
longitudinal ribs armed with small crescent-shaped scales of the same 
colour, towards the margin: within white with a pale orange 
streak extending half way from the hinge to the margin. 14...1— 
EH. Indies. 
C. Retusum. Lin. 1121.—D. p. 112.—Lam. 42.—Ch. ff. 
139, 140, 1, 2.— #. t. 294. f. 2, 3.—W. 1. 5. f. 52.—Heart-shaped, 
white and shining, (or sometimes pale yellow and _ occasionally 
spotted with red,) with about twenty-one longitudinal, crenated 
grooves, whose intermediate ribs are more or less tuberculated ; 
umbones carinated, with a crescent-shaped cavity beneath them 
on the posterior side, within white. I%..14.—Persian Gulf 
and Red Sea. 
C. Tumorirerum. Lam. 43.—C. I. f. 22.—Reeve, t. 77. f. 
22.—Del. t. 11. f. 7. Heart-shaped, inflated, whitish, subquadn- 
lateral, one side obtusely rectangular, the whole of the broad 
flattened ribs nearly smooth: lunule large and smooth. Nem 
Flolland. (Much resembles the next, but the posterior depression 
isnot margined by wrinkles.) 
C. Hemicarpium. Lin. 1121.—D. p. 113.—Lam. 44.—Ch. 
f. 159, 160, 1.—E. t.295. f. .2—W.t. 5. f. 49. Heart-shaped, 
subtrilateral, whitish or pale yellow; tumid and keeled at the 
anterior end; the anterior ribs smooth, the posterior tuberculated, 
and the interstices narrow and marked with impressed dots; the 
lunule margined by coarse wrinkles. 1}. . 1.—JZolluccas. 

1 Mr. Sonerby in the Conchological Illustration, considers the 
C. Auricuta of Forskael’s Fauna Arabica, as distinct from this 
species, although it has usually been considered by Dilwyn, Sc. 
as a variety differing chiefly by its coloured markings. I give the 
description of an authenticated specimen. Subtrapeziform, diago- 
nally divided by rather a sharp ridge, white spotted with pale 
scarlet, with about twenty-one radiating ribs : posterior area slightly 
larger, its ribs nodular and but little elevated, the interstices very 
narrow and transversely crenulated: anterior ribs unarmed, narrower 
and more depressed, with the interstices simple: lunule large, 
deeply excavated, an internal broad cordiform callus, rendering the 
cavity lunate. 13...1. (C. I. f. 47.)—Red Sea. 
