MYARIA. MOLLUSCA. CORBULA. 43 



the reception of the tooth, and insertion of the ligament. Length 

 2 inches, height 1 T 7 T inch, breadth li inch. 



Single valves of this shell are thrown upon our beaches by violent 

 gales ; but I have never heard of any living specimen being taken 

 directly on our coast. At St. George's and Grand Banks, however, it 

 is abundant, and is a favorite food of the cod-fish, from whose stomachs 

 it is taken plentifully by our fishermen. On the English coast it is 

 spoken of as more plentiful than M. arenaria, found at the mouths of 

 rivers. It is not mentioned as an article of food. 



It is very easily recognised by the peculiar manner in which the 

 posterior end seems to be chopped off; sometimes directly across, and 

 sometimes obliquely ; sometimes leaving the posterior portion of about 

 the same length as the anterior, and at other times not half so long. Its 

 membranous tube, when not broken off by the removal of the animal, 

 as it usually is, is quite a curiosity. There is one shell which at first 

 sight resembles it, the Panopda drctica ; but it is gaping at both 

 ends, and has no tooth. 



GENUS CORBULA, LAM. 



Shell inequivalve, inequilateral; hinge with a small, upright, 

 conical tooth in each valve, one received into a pit by the side of the 

 other ; cartilage between the teeth. 



CO'RBULA CONTRA'CTA. 



Shell small, white, valves sub-equal, covered with numerous con- 

 centric, elevated lines; rounded before, somewhat acute behind; 

 basal margin contracted at the middle. 



FIGURE 37. 



State Coll., No. 218. Soc. Cab., No. 1742. 



Corbula contracta, SAY ; Journ. Aca&. Nat. Sc. } ii. 312. 



Shell small, ovate-globose, white, nearly equilateral, shortest 

 and rounded before, narrowed and somewhat pointed behind, 

 basal margin contracted and arched near the middle ; surface 

 beautifully plaited with regular, smooth, rounded, concentric 

 ridges ; beaks rather prominent, inclined forwards ; a distinct 

 angular ridge running from them to the posterior extremity de- 

 fines a broad rhomboidal space ; left valve nearly as large and 



