THE SUTUEE. YAPICES. 281 



more or less oblique ; and flattened, or rounded, or angular, 

 at the sides. When rounded out, they are said to be i7i- 

 flatecl or ventricose. 



THE SUTURE, 



Or seam, which, in the spire, distinguishes one whorl from 

 another, is described as more or less distinct; sometimes 

 marked by a groove, or canaliculated, and sometimes hidden 

 by an after-deposit of enamel. It is even in some cases, 

 instead of being marked by a depressed line, raised by the 

 enamel into a swelling or ridge. 



VARICES. 



In the course of the shell's growth, it sometimes happens 

 that a check takes place ; the increase onwards is for a time 

 suspended ; and the secretion, accumulating round the last- 

 formed layer, becomes a raised ridge, the edge of what is 

 then the aperture. After this is formed, the growth proceeds 

 in a regular way, till another stoppage occurs, another 

 ridge is formed, and so on till the shell is fully formed ; 

 and the last ridge is the peritreme of the permanent aper- 

 ture. These successive ridges remain prominent outside the 

 whorls of the spire, and are named varices. They occur 



