PELECTPODA 595 



2. CoRBULA Bruguiere. Shell small, inequivalve, thick, gaping in 

 front; hinge with an upright tooth in each valve which fits into a pit in 

 the other; siphons short: 75 species. 



C. contracta Say (Fig. 937). Shell 10 mm. long, 6 mm. high, and 

 5 mm. wide, with a broad, rounded anterior and a pointed posterior end; 

 Burface with regular, smooth, concentric ridges: Cape Cod to Florida, in 

 sand and mud. 



Family 2. SOLENIDAE. 



Shell thin, equivalve, long, and narrow, and with gaping ends; liga- 

 ment external; 1 to 3 cardinals in each valve; no laterals; foot large, 

 cylindrical; siphons short, united about half their length: 100 species. 



Key to the genera of Solenidae here described: 



Oi Margins parallel 1. Ensis 



Ca Margins not parallel ; shell elliptical. 



bx Pallial sinus short 2. Siliqua 



6a Pallial sinus very long 3. Tagelus 



1. Ensis Schumacher. Razor clams. Shell very long and narrow, 

 with parallel margins, with a slight bend making the dorsal side concave 

 and the ventral convex ; 2 hinge teeth in the right and 3 in the left valve 

 near the anterior end ; umbo near same end : 14 species ; in shallow water. 



E. directus Conrad (Fig. 938). Shell about 6 times as long as high; 

 ends truncate ; right valve with 1 projecting tooth and an elongated ridge- 

 like tooth back of it ; left valve with 2 projecting teeth and a double ridge ; 



..".? 



Fig. 938 Fig. 939 



Pig. 9S8—Emis directus (Gould). Fig. 939 — Siliqua costata (Gould). 



length 15 cm. ; height 25 mm. ; width 16 mm. ; color yellowish or greenish : 

 Labrador to west coast of Florida, common in the sand, in which it 

 buries itself by a digging motion of the foot. 



E. viridis (Say). Shell about 5 times as long as high; dorsal mar- 

 gin nearly straight; anterior end truncate, posterior rounded; hinge with 



1 tooth in each valve; periostracum light green, glossy; length 5 cm.; 

 height 10 mm. ; width 6 mm. : Rhode Island to west coast of Florida. 



2. SiLiaiTA Miihlfeldt. Shell elliptical, smooth, with a rib extending 

 from the umbo across the shell on the inner surface; pallial sinus short; 



2 cardinals in the right and 3 in the left valve : 20 species. 



S. costata (Say) (Fig. 939). Shell thin, shining, with a greenish 

 periostracum, 45 mm. long, 18 mm. high, 7 mm. wide: Nova Scotia to 

 Cape Hatteras, in the sand in shallow water ; often very common. 



