CARDIACEA. MOLLUSCA. CARDIUM. 91 



Shell very small, fragile, dingy white, nearly orbicular, some- 

 what oblong ; nearly equilateral ; beaks slightly elevated, in- 

 clined inwards ; an obtuse ridge passes from the beaks to the pos- 

 terior point of the shell, rendering this side a little angular ; the an- 

 terior side is shortest and regularly rounded ; surface with about 

 twenty-six rounded ribs, on each of which is a series of equidis- 

 tant, arched scales, most conspicuous along the posterior slope, 

 where they sometimes assume the form of spines ; interior white 

 or flesh-colored, sometimes with a brownish blotch at the pos- 

 terior muscular impression ; furrowed to correspond to the ribs 

 without. Length -f v inch, height T 4 inch, breadth T 3 T inch. 



This very small and pretty species is as common as any other 

 shell in the stomachs of fishes, and may be obtained from them at 

 almost any time. Mr. Conrad obtained his specimens from Mas- 

 sachusetts, and I have never heard of it in any other locality. 



It is usually accompanied by the young of C. Islandicum, from 

 which it is distinguished by fewer ribs, and the scales crossing them. 

 It resembles the young of C. edule so much, as to excite one's suspi- 

 cions that it is not a distinct species. But a careful comparison will 

 show good characters. It is less equilateral and less convex than C. 

 edule, and the posterior termination is quite different. From C. 

 exiguum it differs in not having a .short, diminished anterior side, ele- 

 vated beaks, and a very prominent ridge posteriorly. The whole as- 

 pect of that shell is angular, while our shell is scarcely at all so. If it 

 is the young of any known shell, I think it is that of C. echinatum. 



CA'RDIUM MORTO^NI. 



Shell small, thin, sub-globose, smooth, pale fawn-color, some- 

 times blotched with dark brown ; within striated, bright yellow, with 

 a purplish blotch posteriorly. 



State Coll., No. 192. Soc. Cab., No. 1928. 



Cardium Mortoni, CONRAD ; Journ. Acad Nat. Sc., vi. 259, pi. xi. f. 5, 6, 7. 



Shell small, thin, obliquely sub-ovate, sub-globose ; beaks 

 large and prominent, incurved, nearly central ; posterior side a 

 little produced and directed obliquely downwards ; surface glossy, 

 destitute of ribs or radiating lines, with fine lines of growth, and 



