710 PROCEEDINGS OF THE ACADEMY OF [NoV., 



much more equilateral, and has the lunule and the interspaces 

 between the ribs deeper, and the latter more channeled. It has 

 17-18 ribs crossed by rounded concentric ridges with the radial 

 channels sharply cross -striated. There are also marked differences 

 in the hinge, which is much more delicate than in V. ventricosa. 

 It has not yet been reported living, but is noted here because it has 

 been united with some of the recent species by Gabb and Cooper. 



Venericardia (Cyclocardia) incisa Dall, 1902. 



Aleutian region, from Unalashka to the Semidi Islands, in 6 to 75 

 fathoms, sand or mud, Dall. 



Shell small, with a polished yeUowish-olive periostracum, with 

 18-20 flat radial ribs separated by linear incised sulci, and crossed 

 by similar concentric sulci ; interior white, often with a yellow flush 

 in the cavity of the valves. 

 Venericardia (Cyclocardia) alaskana Dall. 



Arctic Ocean, north of Bering Strait, from Point Barrow south 

 to the Strait and Bering Sea, the south coast of the Okhotsk Sea, 

 the Aleutian Islands, and eastward and southward along the Alaskan 

 coast as far as the harbor of Sitka, in depths varying from 7 to 

 313 fathoms, with a bottom temperature from 35° to 46.2° F. 

 Also North Japan, in 4-7 fathoms 



This species is that which from the Pacific has usually been 

 named V. borealis Conrad, and I can only ascribe the long accept- 

 ance of this determination, made by Dr. Carpenter, to the absence 

 of a good series of the Eastern shell. After comparing them no 

 one can hesitate to separate them specifically. There is a distance 

 of several thousand miles between their nearest points of approach 

 to each other in range, as far as known. In a general way, until 

 Dr. Stearns looked into the matter ,in 1890, all the Pacific Cy- 

 clocardias were lumped together under the name of borealis Conrad. 



The present species is ovate, compressed, with 23-25 uniform and 

 elegant radial ribs with narrower interspaces, distinct to the margin 

 of the shell and covered with a dark yellow -brown velvety perios- 

 tracum, the hairs in close radial lines. The ribs are slightly granu- 

 lar near the low beaks ; the lunule narrow and long. The hinge is 

 solid, with the right anterior and posterior cardinals nearly obso- 

 lete ; the interior is chalky white and is figured in the Proc. U. S. 

 Nat. Mus., XIII, PI. XVI, fig. 8, under the name of C. borealis. 



