VO l8S9. n '] PROCEEDINGS OF THE NATIONAL MUSEUM. 255 



species, as in the Y. solenoides, there is a narrow lunule and escutcheon 

 bounded by a shallow groove, but in the latter this groove indents 

 the anterior margin, while in Y. scapania it does not. There are a few 

 obscure radiations, and the incremental lines are more conspicuous 

 toward the middle basal part, but the sculpture, if such it can be 

 called, is hardly noticeable. The teeth are larger in Y. solenoides, though 

 it is a much smaller shell. 



Yoldia pompholyx Dall. 

 Plate xm, Fig. 8. 

 Yoldia pomphohjx Dall, Bull. U. S. Nat. Mus. No. 37, p. 44, No. 151, 1889. 



Shell small, rounded, polished, inflated, smooth except for incremen- 

 tal lines, covered with an extremely thin grayish green epidermis; sub- 

 translucent when fresh, ashy or white when weathered ; a pair of very 

 faint ridges in front of and behind the beaks indistinctly indicate areas 

 corresponding to lunule and escutcheon; beaks rounded, inconspicu- 

 ous; shell entirely closed when the valves are shut; ligament nearly 

 central, its upper surface slightly exposed externally between the valves ; 

 interior smooth ; hinge line narrow, roundly arched with seven anterior 

 and eight posterior teeth of normal form and a well-marked pit or 

 fossette central between the beaks; margins smooth ; maximum longi- 

 tude of largest valve 4 miu ; longitude of another (pair) 3.5; altitude 3; 

 diameter 2 mm . 



Hab.— U. S. Fish Commission Station 2668, in 294 fathoms, gravel, off 

 Fernaudina, Fla, ; temperature 4G°3 F. Also by Dr. W. H. Bush, U. S. 

 Navy, off Havana in 1,024 fathoms, mud, and off the Fowey Eocks, east 

 Florida, in 205 fathoms. 



This curious little species has much the external form of Jeffreys' 

 Glomus, but has the regular hinge of the small rounded Yoldias. 



Genus LED A Schumacher. 

 Leda cestrota sp. nov. 



Plato xm, Fig. 7. 



Shell thin, compressed, elongated, rostrated, translucent white, with 

 a pale gray or olive epidermis, which is generally mostly lost; umbones 

 hardly raised above the hinge-line, pointed, inconspicuous, compressed; 

 base forming a shallow reversed arch, meeting the anterior curve of the 

 upper edge in a rounded point; posterior upper margin nearly straight, 

 becoming slightly concave toward the end of the rostrum; rostrum 

 longest above, obliquely truncate, its basal margin slightly concave, 

 then swelling into the curve of the base ; sculpture of numerous thin, 

 sharp, elevated concentric lainellse, prominent anteriorly and near the 

 base, less so on the cheeks of the valves and obsolete near the rostrum; 



