226 
In the Devonshire whetstone -pits, a shell is found, measuring from 
three to five inches in width ; and which, I suspect, from the parti- 
cular oblique turn of its beak, and from so much of the hinge as I have 
been able to expose, belongs to this genus. This shell is very unequal 
sided, and the upper part of its produced side has been set with minute 
spines, regularly disposed. 
CL. Anomia. An irregular shell, with unequal valves ; the inferior 
valve pierced or notched at its beak, which is sometimes closed by a 
little operculum, or third valve, attached to a cartilage passing out ot 
the hole or notch, and serving to fix the animal on other bodies. The 
hinge without teeth. 
With the shells of the genus Anomia, as formed by Linnaeus, Bru- 
guiere and Lamarck have composed six genera : Anomia , P lacuna, 
Crania, Terehratula , Calceola, and Hyalcea. 
The shells of the present genus differ from others chiefly in possess- 
ing a valve or operculum, with which the animal fixes itself to adjacent 
bodies. This circumstance, it is to be observed, can only be ascer- 
tained in the recent shell ; and therefore cannot be called into aid, 
when comparing the fossil shells of this genus with those of Terehra- 
tula ; since, each having an opening in the under valve, there exists 
no particular difference in that state ; excepting, that the shells of the 
genus Anomia are more rude and irregular than those of Terehratula. 
I am therefore unable to point out any fossil shell which shows any 
proof of having possessed the characteristic valve or operculum of this 
genus. Anomia ephippium, Linn. List. Conch. Tab. 204, Fig. 38, is 
instanced as a species of this genus. 
CLI. Crania. A regular inequivalved bivalve : the lower valve flat 
and nearly round, and pierced in its inner face with three unequal 
and oblique holes ; the upper very convex, furnished interiorly with 
two projecting callosities. 
These shells had been ranged among the Anomiae, and formed the 
Anomia craniolaris, Linn. ; but Bruguiere and Lamarck considered 
