OF CONCHOLOGY. 25 



preceding, both in genera and spe- 

 cies ; and it requires a considerable 

 decree of attention, to discriminate 

 many of the species, as they run into 

 each other so much ; and of many of 

 the species there are several varieties. 



It is by the general outline that the 

 shells of this order are distinguished, 

 together with the formation of the 

 spire, and aperture ; from their having 

 a canal or gutter, the pillar-lip, and the 

 outer-lip being expanded, together 

 with the notches, <&c. on the outer 

 surface ; the colours also, are of ser- 

 vice in describing species, though it 

 cannot in all cases be depended on, 

 many of them being subject to great 

 variety. 



Linnaeus divides his Order Univalve 

 into two sections, turbinated shells 

 within a regular spire, and those with- 

 out any regular spire. 



Apex. The summit or highest part 

 of the spire. Plate 2nd, AAA. 



E 



