S86 



SHELLS AND SHELL-FISH. 



Inoceramus Sow. Cardiform, thick ; umbones lateral, 

 rather prominent, and incurved ; hinge short, formed 

 of a series of short transverse grooves : the cardiform 

 type. 



I. Lamarck ii. Sow. Man. f. 167. 



Malleus, Shell very irregular, more or less hammer- 

 shaped ; the hinge margin being straight, and often 

 greater prolonged ; the valves gaping to near the 

 umbones. 



Malleus Lam. Hinge margin excessively long, and 

 forming two auricles ; umbones minute, depressed;, 

 with a small disk for the liga- 

 ment, and an external groove for 

 the cartilage. 



M. vulgaris. Sow, Man, 167. 



Reniella Sw. Shell transversely 

 and irregularly orbicular ; sub- 

 ventricose near the umbones, 

 which are very small, termi- 

 nal, and remote; between them 

 is a deep triangular concave pit, 

 lined by the ligament ; the mar- 

 gin of this pit forms a semicircle, 

 to the edge of which is attached 

 a narrow cartilage. 



R. dilatata Sw. {Jig. 127.) 



Vulsella Z,am. Shell tongue- 

 shaped, longitudinally elon- 

 gated, compressed, without 

 auricles ; umbones minute, 

 curved, approximating ; 

 hinge plate thick, diluted 

 into a semicircular solid pit 

 for the cartilage. 



V. lingulata. Sow. Man, 



AvicuLA. Shell regular, foliaceous, unequally auricu- 

 lated; hinge margin straight, much lengthened 



