FAMILY MYAD.E — COEBULA. 241 



lobe on the edge : valves ridged by the stages of growth, convex ; beaks moderately prominent. 

 Color : epidermis yellowish ; beneath white. Length, 1 • 5 - 2 • 5 ; width, 2 • 5 - 3 • 5. Common 

 on the Grand Banks : a few valves occasionally found on the shores of Massachusetts. 



GENUS CORBULA. Bruguieres. 



Animal unknown. Shell moderately solid, subtrigonal, inequivalve, inequilateral, slightly 

 gaping. Hinge with a small conic erect recurved tooth in each valve, one received into a 

 pit by the side of the other : cartilage between the teeth. Palleal impression feebly exca- 

 vated. 



CORBULA CONTRACTA. * 



PLATE XXVm. FIG. 285. 



(STATE COLLECTION.) 



Corbula contractu. SAY, Jour. Acad. Nat. Sciences, Vol. 2, p. 312. 

 C, id. Gould, Invertebrata of Mass. p. 43, fig. 37. 



Description. Shell small, solid, convex ; valves subequal, shortest and rounded in front, 

 long and pointed behind. Beaks rather prominent, nearly touching each other at their points : 

 basal margin contracted and concave in the middle. Surface with regular equidistant con- 

 centric impressed lines and intervening ridges. A prominent ridge runs from the beaks on 

 each side to the posterior basal margin, including a broad space between them : left valve 

 shutting within the other along the basal margin. Epidermis thin. In one valve the tooth is 

 simple, hooked and turned towards the beak ; in the other, it is broader than high, project- 

 ing at right angles to the valve, with a deep cavity on the posterior side of the base for the 

 reception of the hooked tooth. 



Color. Epidermis dull brown ; beneath dead white. 



Vertical axis, - 25 ; transverse ditto, 0*4. Diameter, 0'2. 



This little shell is not uncommon along our coast, from Florida to Cape Cod. I hare 

 found it on the shores of Long island, and Mr. Linsley of Stratford has sent it to me from 

 the shores of Connecticut. The epidermis is occasionally ferruginous. 



Fauna — Part 6. 31 



