166 AMERICAN MARINE OONCHOLOGY. 



2. G. FASTIGIATA. Gould. 



Bost. Proc., viii. 280. 1862. 



Shell small, obliquely triangular, rather solid, yellowish, concen- 

 trically sharply ribbed ; apex acute, anterior margin concave, 

 dorsal margin arcuate ; ventral margin nearly straight, anterior 

 angle distinct, posterior angle rounded. 



Length and height 8 mill. 



Frying Pan Shoals, N. Car. 



I have not seen this species, nor has it been figured. 



Genus CAKDITA, Brugiiiere. 

 Encyc. Meth. i. 401. 1789. 



Animal with the mantle-lobes free, except between the siphonal 

 orifices; branchial margin with conspicuous cirri; foot rounded 

 and grooved, spinning a byssns, labial palpi short, triangular, 

 plaited, gills rounded in front, tapering behind, and united 

 together, the outer pair narrowest. 



Recent systematists have separated a number of genera from 

 Cardita, and generally, with sufficiently good distinctive char- 

 acters; I have indicated these groups in the specific descriptions. > 



1. C. BOREALIS, Conrad. Fig. 422. 



Am. Mar. Conch., 39, t. 8, f. 1. 1831. 

 Cardita vestita, Deshayes, Zool. Proc., t. 17, f. 10. 1852. 



Shell suborbicular, thick, with about eighteen rounded ribs, and 

 narrow interstices, concentrically striated; epidermis brownish- 

 black; margins crenulated within. 



Length and height 1 inch, diam. .T inch. 



New York, northwards. 



This is the Jype of Conrad's genus Cyclocardia, which also 

 includes the following species. 



2. C. NOVANGLI^B, Morse. Fig. 423. 



(Cyclocardia.) First An. Rep. Peabody Acad., 76, f. 1869. 

 Shell oblong ovate, thin, beaks nearly central, not prominent; 

 with about seventeen ribs and concentric striae; margin crenate 

 within. 



Length 21, height 16 mill. 



New England, northwards. 



This species is more transverse and thinner than C. borealis, 

 the beaks are not so elevated or projecting, and the hinge-plate is 

 much narrower. 



