112 THK NAUTILUS. 



to identify one of these shells, sent in from Monterey by Mr. Berry, 

 all the available specimens were brought together and carefully com- 

 pared, leading to the conclusion that the shell is a distinct species. 



Cardium ( Cerastoderma ) fucanum n. sp. 



Shell small, plump, compact, solid for its size, covered with a 

 smooth brown or gray periostracum usually more or less eroded ; form 

 varying from nearly circular to slightly ovate, with rather prominent 

 slightly prosoccelous beaks, situated a little anterior to the middle of 

 the shell ; valves moderately convex, equal and nearly equilateral, 

 sculptured with numerous (40 to 58) similar, small, low, flatfish radial 

 ribs separated by much narrower interspaces ; these ribs are not 

 nodulous nor keeled, they are sometimes slightly rippled by the in- 

 cremental lines, and, as usual, are smaller, fainter and more crowded 

 distally ; the interspaces are rounded ; near the dorsal margins on 

 each side of the beaks there is an ill-defined narrow space which is 

 devoid of ribs ; the average number of ribs is about 50 ; the inner 

 margins of the valves are crenulated ; the hinge delicate and normal ; 

 the inner surface of the valves white, polished ; the outer surface 

 usually shows three or four concentric sulci due to resting-stages. 

 Length 38, height 33, diameter 18 mm., of a fully adult specimen ; 

 a shorter variety measures 25.5, 24.5 and 16 mm. for the same di- 

 mensions. 



From Bering Sea (in 70 fathoms, temperature 39.0) south to 

 Monterey Bay, California (in 20 fathoms); the depths varying from 

 20 to 70 fathoms and the temperatures from 39.0 to 52.3. Col- 

 lected by Kennerley, Swan, the U. S. F. Com. Str. Albatross, and 

 Mr. S. S. Berry, of Stanford University. 



This species somewhat resembles C. hayesii Stimpson from the 

 Arctic Sea but has more numerous and more uniform ribbing. It 

 wants the angulation (in fresh specimens fringed with periostracum) 

 which is characteristic of G. ciliatum Fabr. in the young stages, and 

 has more, and more crowded, ribs, and a more solid shell. It is 

 most nearly allied to C. californiense but has a thicker and more 

 ventricose shell, is less attenuated posteriorly and less oval in form, 

 the ribs are more closely adjacent and more uniform in size than in 

 californiense ; though the number is about the same the diminutive 

 size of fucanum makes them appear much more numerous. Most of 

 the 14 specimens examined came from the Straits of Fuca. 



