94 EOCENE MOLLUSCA. 



sulangidatd ; area conncxds angustd ; sulcis raris exaratd ; marginibus denticulatls ; 

 dentibus Jateralibus tribus. 



Shell transverse, ovately oblong, inflated, thick, oblique, and inequilateral, striated and 

 decussated, slightly compressed in the middle of the shell; pedal region short ;.ligamental 

 area rather narrow, with few and obsolete chevron-form marks; margins denticulated, 

 three lateral teeth on each side. 



Length, 2\ inches; breadth, li inch. 



Localities. Faversham (Crowe), Heme Bay, Richborough, Oakwell, near Faversham, 

 Nash Park, near Bough ton (Prestcvich). 



This shell is considered by Professor Morris, in his ' Catalogue of British Fossils,' as 

 identical with Cucidlaa crassatina, Lamk. ; but, although there is a very close approxima- 

 tion, I am doubtful of their identity ; and, as I am not imposing a new name, I prefer 

 the British fossil should remain with the one under which it was figured and described by 

 Parkinson and Sowerby. 



On a comparison of the English shells with specimens in my own cabinet from 

 Beauvais, I find the following differences : — The French shells appear to be more inflated, 

 and they have a more prominent, angular, and distinct ridge diagonally across the 

 syphonal region, and the English shells are comparatively longer ; neither can I see the 

 great inequality between the two valves which is so conspicuously shown in the French 

 specimens ; the rays upon our shell are large, wide, flat, and bipartite, and these rays are 

 more nearly alike upon^the two valves than are thoseof C. crassatina. The dental area is 

 furnished with a few teeth at each extremity of the line ; those on the siphonal side are 

 about three or four in number, and parallel with the hinge-margin ; at the opposite ex- 

 tremity there are about the same number, and they are also inclined ; all of them are 

 vertically striated, or rather denticulated, but more finely so than are either of the French 

 species, and in the centre of the hinge-line are a few small teeth in a vertical direction ; 

 these are also finely nodulous ; the margin is crenulated by the outcrop of the rays. 



PECTUNCULUS, Lamarck; 1789. 



Gen. Char. Shell equivalve, orbicular, convex, or lenticular, nearly equilateral, smooth, 

 or radiately striated ; umbones central, generally distant, divided by a striated area for 

 connexus, which is wholly external or ligamental ; hinge with a curved row of transverse 

 or angular denticles; adductors nearly equal, palleal line simple, margins crenulated ; the 

 shells in the living state are generally covered by a thick and velvety epidermis. 



Animal with the margins of the mantle simple, sometimes studded with minute ocelli; 

 foot large, crescent- shaped, capable of considerable expansion, so as to form a disc, on 

 which it is said to be able to move; this foot is supplied with retractor-muscles, the im- 



