294 BULLETIN OF THE 



be true of all species, for the gills of mollusks are largely mere modifications 

 of the cutis and very mutable structures. 



Since the publication of ray preliminary paper on the Blake Mollusks, I 

 have had the advantage, for the Pelecypods especially, of being able person- 

 ally to examine the species comprised in the Jeffreys collection, including 

 specimens of the deep-water forms known to me previously oaly by description. 

 In this way, and by the aid of the valuable labors of Mr. E. A. Smith, pub- 

 lished in the Challenger report, I have been able considerably to improve upon 

 previous work, in a manner which would have been impracticable under other 

 circumstances. Otherwise, in many cases I coflld express opinions, on the 

 present group especially, only with reserve not unmixed with doubt. 



The sections or subgenera represented in the Blake collection now follow. 



SUBGENDS CUSPIDARIA, 8. 8. 



Shell usually concentrically sculptured, with or without a buttress; fossette 

 posteriorly inclined and attached to the hinge-margin by its posterior edge; 

 one posterior lateral tooth in the right valve. 



The following species in addition to those examined by Smith belong here: 

 C- arctica Sars, C. glacialis Sars, C. lamdlosa Sars, C. exigua Jeffreys, C. Jef- 

 freysi Dall. C. limatula Dall {contracta Jeffreys) has no teeth. C. arcuala 

 Dall, being described from a toothless left valve, is still in doubt. 



A valve of C. glacialis Sai-s, dredged in 1467 fms. in the Gulf of Mexico by 

 the U. S. Fish Commission, is 45.0 mm. long, 28.0 mm. high, and the com- 

 plete shell must have been about 30.0 mm. in diameter. 



Cuspidaria rostrata Spengleb. 

 NeoRra rostrata Spengler, Dall, Bull. M. C. Z., IX. p. Ill, 1881. 



Habitat. Barbados, 100 fms. ; Station 36, 84 fms.; Sand Key, 80 fms. 



No additional specimens of this species have turned up in the Blake collec- 

 tion since the above were noted. It has been dredged in from about 65-500 

 fms. in various localities from the West Indies northward. Among the Mu- 

 seum specimens are two very large dead and rather worn valves from Stations 

 2659 and 2660 of the U. S. Fish Commission, off Cape Canaveral, in 509 and 

 504 fms., bottom temperature 45°. 2 and 45°. 7 F. respectively. They differ 

 from the typical form in ha\'ing the rostrum proportionally more slender, 

 shorter, and curved, the dorsal margin being quite concave, and especially in 

 having the dorsal surface very wide and with a wide strongly marked de- 

 pressed area extending from the beak to the tip of the rostrum, smooth or 

 longitudinally striate. The surface of the valves was dark brown apparently, 

 and strongly concentrically striate. The valves are proportionally much more 

 compressed than in the usual form of C. rostrata. The dimensions of the best 



