OSTREA. 
S6 
Linnsean arrangement is professedly founded on the 
shells; and therefore, when the hinge is much of 
the same description, and the other characters are not 
absolutely incongruous, it is surely unnecessary to 
divide them otherwise than into sections, accord- 
ing to their natural conformation. Neither, in 
fact, are all the varieties of the species in each 
division extremely dissimilar ; for it is not at all 
uncommon to meet with specimens of the common 
Oyster, Ostrea ediilis, of a pectinated and eared 
form ; so that a regular transition might be shewn 
from one to the other family. The third division 
C. is connected to the former ones by the O. Pes 
LutrcB, which partakes largely of the properties of 
both; and dilfers from the 3d subdivision of A. 
only in the shape and direction of the groove 
which constitutes the hinge, and in the thickness 
of the valves, which renders it not unlike the 
division B. 
Strong locomotive powers have been attributed 
to the Pecten, which are, it is said, exerted in a 
most singular manner. A very rapid progress is 
effected by the sudden opening and closing of the 
shell. This is done with so much muscular force. 
