Fam. 7.] NATURAL HISTORY SOCIETY. 91 



long row of teeth divided into two sets by a pit for an internal 

 cartilage ; pallial line entire. Animal with open, plain-edged 

 mantle; foot large forming when expanded a disk with notched 

 margins ; mouth minute ; palpi very large and furnished with 

 long convoluted appendages ; gills small, feather like. 

 1. NucuLA, Lam. 



Shell small, somewhat triangular, with the umbones turned 

 toward the short (posterior) end, closed ; hinge line curved or 

 angular, with a distinct cartilage pit separating the line of small, 

 sharp teeth on each end. 



Animal with plain edged mantle ; foot large, forming, when 

 expanded, a disk with serrated margins ; palpi very large, and 

 protruding from the shell with the foot; gills small, plume-like. 

 Inhabitants of rather deep water (2 to 100 fathoms) and so are 

 rarely thrown on shore; often found in the stomachs of fishes. 



1. Nucula proxima, Say. Shell oblique, ovate-triangular, crossed 

 by minute, concentric and radiating lines ; umbones prominent ; 

 hinge teeth about 12 behind and 18 before the small cartilage 

 pit ; the two series of teeth form nearly a right angle ; inner edge 

 finely crenulated. Epidermis light olive; interior, pearly. L. 

 10 ; H. 9 ; W. 6 ; U. | ; An. 85°.— Whole coast. 



2. Nucula delphinodonta, Migh. Shells oblique, ovate-triangu- 

 lar, tumid ; hinge with 3 teeth behind and 7 before the cartilage 

 pit; a deep heart-shaped excavation in front of the umbones 

 bordered by a ridge. Epidermis olive. L. 3}; H. 2f ; W. 2J 

 U. f ; An. 100°.— New England. 



Family 7. LEDID/E. 

 Shell more elongated than in the preceeding family, rounded 

 in front and extended and somewhat }>ointed behind ; teeth of 

 the hinge many, divided by a cartilage into two sets ; pallial 

 line with a small or large sinus. Animal with partially or 

 wholly united, elongated siphons ; gills narrow, feather-like ; 

 palpi large. 

 ^ Pallial sinus large ; cardinal teeth of the two ends about equal in number. 



1. Yoldia. 



* Pallial sinus small ; teeth of the posterior or narrow end about ^ more 



than the anterior 2. Lecla. 



1. Yoldia, Mor. 

 Shell oblong, compressed, gaping behind, smooth and shining ; 



