1 INTRODUCTORY CHAPTER. 



L9 



ferent kinds of shells, with a description of the parts con- 

 stituting them, and the names by which they are known, as 

 in giving an account of the variations which exist in the 

 different genera many of these will be referred to. In fig. 1. 

 is delineated the simplest form amongst univalves, that of a 



WmvaJm the!/.*. 



Patella, in which the parts necessary for reference are but 

 few. A is the apex, B the mouth or aperture, of which CC 

 is the margin. The exterior and interior are sufficiently 

 obvious. In figures 2. to 7., which are turbinated or spiral 

 shells, and of a more complicated form, a greater number 



c 2 



