98 
t. 11. f. 1.—Turt. B. p. 188.—F. p. 422.—Rounded- 
heart-shaped, becoming obliquely heart-shaped from 
the anterior side being produced by age, dirty white, 
with about twenty-six ribs which are rough with trans- 
verse wrinkled subimbricated strize; inside white, 
stained anteriorly with brown. 14. 
cockle. 
The common 
C. Fasciatum. Mont. Sup. p. 30. t.27. fi 6.— 
Pen. 4. p.191.— Wood. G. C, p. 215.—D. p. 130.— 
Turt. C. D. p. 32.—Turt. B. p. 189.—F. p. 422.— 
(the young of C. Rusticum. fide. Sow. in C. 1.—Or- 
bicular flattish, semitransparent, yellowish or pale 
rufous, glossy, with a few dark transverse bands often 
disposed in spots on the ribs. Mot uncommon. 
*** Ribs unarmed. 
C. Mepium. Lin. 1122.—Lam. 40.—CA. f. 162, 
3,4.—E. t. 296. f. 1.—Pen. 4. p. 186.—Don. 1. t¢. 
32. f, 1.—Mont: p. 83.—Lin. T. 8. p. 61.—Wood. 
G. C. p. 211. t. 50. f. 3.—D. p. 113.—Turt. C. D. p. 
32.—Turt. B. p.190.—F. p, 422.—Tumid, suborbi- 
cular, rather truncated anteriorly, yellowish white, with 
reddish brown blotches, about fifty radiating ribs which 
are rather obscure in the middle but stronger at the 
