68 
A NO M I A. 
A. Perforated in the apex. (Plate X. Fig. 1.) 
B. Perforated in the disk, (Fig\ 2.) 
C. Imperforate. 
Shell inequivalve ; one valve flatter, the other 
more gibbous, often produced and incurved towards 
the beak. One or both valves are frequently per- 
forated near the apex. Hinge toothless, consisting 
in some species of a prominent linear callus or ci- 
catrix, with or without one or two internal mar- 
ginal teeth, and two bony rays in the cavity. 
Shape orbicular or obovate, rarely quadrilateral. 
The definition of the Anomia, given by Linnseus, 
is very unintelligible : it is therefore attempted to 
render it less so, by altering some parts of the 
description which appear unnecessary and tend 
only to obscurity. This genus in fact comprehends 
species ditfering so greatly in essential characters, 
that it is hardly possible to form a description 
which shall not be contradicted by some among 
them. The perforation in one or other of the 
valves, for the emission of a ligature, by which the 
