16 THE ELEMENTS 



ostrea, anomia, and pinna, have in 

 general dissimilar valves. The first 

 of these kinds are called equivalve, 

 and the latter inequivalve. 



Equilateral shells are those whose 

 sides are alike, as in the shells of 

 ostrea, commonly termed scallop- 

 shells in England, or those shells worn 

 by pilgrims in former times ; 



" And fix'd the scallop on his hat before." 



Parnell. 



This is also exemplified in the 

 Area Glycimeris and Pilosa of Lin- 

 naeus. 



Inequilateral valves are shells whose 

 sides are unequal ; and are of different 

 shapes, as in the mactra, donax, &c. 



Summit is the most elevated point 

 of that part of the shell in which the 

 hinge is placed ; plate 1st, fig. 4 & 8, 

 a a. 



In naming this the summit, we do 

 not follow the axiom of Linna3us, but 

 that of a modern author whose autho- 



