90 INVERTEBRATA OF MASSACHUSETTS. 



ed, and regularly wrinkled by the lines of growth ; epidermis yel- 

 lowish-brown, lax, and bristling into a stiff fringe on the sharp 

 edge of the ribs ; within straw-colored, the portions covered by 

 the mantle pearly ; grooves, answering to the ribs without, are 

 obvious within, and the edges are strongly notched. Length 2 

 inches, height somewhat less ; breadth 1 inch. 



Found plentifully in the stomachs of fish caught in Massachu- 

 setts Bay. 



This shell seems not to have been hitherto described, in all its char- 

 acters, by any one writer. English authors seem to have possessed 

 superannuated specimens, which had lost the epidermis ; and such we 

 have long been in the habit of receiving from the Bank fishing-grounds. 

 On the other hand, Mr. Couthouy, having only immature specimens, 

 failed to trace their pedigree. Through the kindness of Dr. Storer, 

 I have had an opportunity to examine specimens of Mr. Couthouy's 

 C. pulescens of the size above indicated, taken in our Bay, covered 

 with their peculiar epidermis ; under which disguise, however, it was 

 not difficult to detect the C. Isldndicum. A few years since, I exam- 

 ined a denuded specimen, brought by Dr. C. T. Jackson from the 

 coast of Maine, where he says they are not uncommon, measuring 

 2^ inches in length, by 2^- in height. Those taken in Massa- 

 chusetts Bay seldom exceed half an inch in diameter. 



Destitute of an epidermis, it looks much like C. edule, but is easily 

 distinguished by the number of ribs. In two of my specimens there 

 are thirty-eight ribs ; in all the others there are thirty -six ; C. ediile has 

 twenty-six. It is usually found in company with C. pinnulatum, and 

 would not be readily discriminated from it. But, besides the greater 

 number of ribs, its bristled fringe upon the ribs, instead of little tuber- 

 cles, marks it. It closely resembles C. exiguum also ; but, among 

 other obvious differences, that shell has an angulated form. 



CA'RDIUM PINNULATUM. 



Shell small-) sub- orbicular, with a slight angle posteriorly, sub- 

 equilateral ; surface with twenty-six ribs, with a single range of 

 arched scales upon each. 



FIGURE 57. 



State Coll., No. 191. Soc. Cab., No. 2336. 



Cardidm pinnulatum, CONRAD ; Jonrn. Acad. Nat. Sc., vi. SCO, pi. xi. f. 8. 



