12 TERMS UNIVALVES. 



turned towards you, the front of a univalve is 

 seen ; reverse it, and you see the back. 



" The top, or highest part, is tli€ /^^ ; (a) 

 the lowest part is the base of the shell, (b.) 



*' The spii-e (c) is formed of wreaths, or whorls^ 

 (ddd) which terminate in the apex : the lowest 

 whorl is the body of the shell, (e.) 



" The aperture, opening or mouth, (/) as it is 

 sometimes called, is on the right hand when the 

 front of the shell is turned towards you. The 

 aperture is an important distinction in univalves : 

 some genera have a circular opening, as the 

 Turbo, or periwincle ; some longitudinal, as the 

 cowry ; others semi-lunar, as the Helix, or snail 

 genus. (For examples of these apertures see 

 Plates 1 and 70 



" The beak is the lengthened process (g) at 

 the lower part of the shell. 



" The canal, ox gutter, runs through the beak. 

 (Both these parts are perceptible in Murev and 

 Strombus, Plate 7-) 



" Sutures are spiral lines which separate the 

 whorls ; they are sometimes crenated, or notched, 

 sometimes sulcated^ or furrowed^ 



" The columella, or pillar, extends through 

 the centre of the shell withinside. The Buccinum 

 and Voluta both show the columella. (Plate 3.) 



" The pillar-lip of the aperture, or columella 

 margin, is on the left-hand side of the shell ; the 



