436 VENERID^. 



dining. The anterior side is very much the smaller, being 

 hardly more than half the size of the posterior, its ex- 

 tremity is rather narrowed, and is rounded Loth above and 

 below. The hinder termination is broad and sub-bian- 

 gulated ; the posterior margin being somewhat straightened 

 in the middle, and its inclination almost perpendicular, 

 though slightly bending forward inferiorly. The umbones 

 are rather swollen and prominent ; the beaks acute and in- 

 curved ; in front of them is a dorsal depression, but no 

 defined lunule. The ligament is large and broad, but not 

 at all projecting ; there is no excavation or depression of 

 the hinder dorsal surface. The interior is white, the mar- 

 gin acute, entire, and decidedly flexuous. The hinge, con- 

 sidering the fragility of the valves, is rather strong, and 

 consists in the right valve of two divergent primary teeth, 

 of which the hinder is bifid, and the front one simple ; and 

 in the left valve of three divergent cardinal ones, of which 

 the central is much the largest, and very profoundly bifid, 

 or rather reversed V- shaped, and the others simple and 

 extremely narrow. The pallial sinus is very large, and 

 runs slightly obliquely into the middle of the disk. 



The average breadth does not much exceed an inch and 

 a quarter, and the length is slightly superior. Although 

 there is no difficulty in procuring dead examples of this 

 interesting shell, we seldom meet with it in the living state, 

 probably owing to the nature of the localities in which it 

 buries itself. During the winter season it is occasionally 

 thrown alive on the shore by storms, but is rarely so taken 

 in the dredge. Only very recently have we been able, 

 after many endeavours, both of our own and of numerous 

 indefatigable friends, to obtain sufficient information re- 

 specting its animal constructor — one of the many obliga- 

 tions we owe to our invaluable correspondent Mr. Clark. 



