TRIBE CARDIACEA. 139 
under a yellowish epidermis, white spotted with brown and red ; 
with thirty-two ribs of which the posterior are biangulated and 
crenated, the central smooth and sede Me bs anterior rounded 
smooth and armed with oblique tubercles. 27,..144.—W. Indies. 
C. Macutatum. C. I. f. 18.—C. oo uclaett, Sow. Z. P. 
1833. Oboval, subventricose, anteriorly somewhat sloping, marbled, 
with radiating ribs of which the posterior ones are flattened and 
their edges crenated, the anterior ones rounded: the interstices 
posteriorly very narrow. 21..1,3,.—California. 
C.Enopr. Son. Jun. Z. P. "1840. —C. I. f.51. Oval, ven- 
tricose, anteriorly subexpanded, most strongly toothed ; pale ful- 
vous with rosy bands ; within white, yellow under the umbones, 
purple at the margin: with thirty-eight flattened ee ee posterior 
slightly crenated, the interstices very narrow. 23. .23,.— Ceylon 
C. Nutratu. Conr. Journ. A. N.S. Phil. 7. p. 229. t..17. 
Jj. 3. Ovate triangular, ventricose, thick, with thirty-four regu- 
larly rounded ribs with prominent arched strive ; umbo narrowed, 
summit very prominent ; anterior slope much depressed ; anterior 
margin straight, oblique, simply undulated ; ligamental margin de- 
clining, ventral edge regularly arcuated ; white with a yellowish 
brown epidermis : lateral teeth thick and prominent, margin pro- 
foundly serrated. Length 33.—N. California.' 
C. QuapRAGENARIUM. Conr. Jour. A. N. S. Phil. 7. p. 
230. ¢.17. f. 5. Cordate, subequilateral, ventricose, thick, with 
forty to forty-two prominent subangular ribs, which are flattened 
at the side and armed with a row of small tubercles; these 
largest on the posterior side where they are seated on the middle of 
the ribs, though elsewhere on the anterior angular margin ; umbo 
broad and prominent ; beaks not oblique, tubercles elevated on the 
anterior slope: pale yellow with fulvous spots and zones: anterior 
margin direct, deeply serrated. . Length 3.—U. California. 
Allied to Asiaticum. 
C. Catrrornianum. Conr. Jour. A. N.S. Phil. 7. p. 229. 
t. 17. f. 4. Suborbicular, ventricose, thickish, with thirty-four 
prominent slightly flattened ribs roughened by prominent arched 
strize which become obsolete on the back of the ribs in the middle 
of the valves: summit of the umbo prominent, beaks, oblique ; 
yellowish with pale red spots: margin deeply serrated : anterior 
margin direct and undulated. Diam. 13.—U. California. 

1 Compare the young of Nuttalii, with the C. Arcriéum. Sow. 
Jun. Z. P.1840.—C. I. f. 26. Oval, compressed, subequilateral ; 
with twenty-seven angular subcrenulated ribs ; the epidermis thick 
and olive brown (becoming by age eroded at the umbones) ; ligament 
elongated : central teeth obsolete, lateral distant. 12.. i 11, 
Arctic Ocean. SOE 
