﻿FRESH-WATER SHELLS. 



having a spiral turn or twist are called snail shells, and arc 

 to be studied Urst. 



3. Let the pupils pick out from their collections the 

 shells like these : 



Fig. 8.— Fuesh- Watee Snail-Shells. 



The different spiral turns, or twists, are called wJiorls, 

 and the whorls together form the sjpire. The opening into 

 the shell is called the ai^erture^ and the line separating the 

 whorls is called the suture. The pointed end of the spire is 

 called the aj)ex, 



apex. 



suture. <•-"--- 



body-whorl. 



^chorh formiug tlie spire. 



aperture. 



Fig, 4. — Suelt., -with Parts namei>. 



