CHAPTER IX. 



SNAILS AND OTHER UNIVALVE SHELLFISH. 



Snails can be picked up anywhere on the seacoast, in ponds 

 and riTers, or in damp places on land under sticks or leaves. 

 Our common large land-snail is called Helix aliolabris 

 (Fig. 71), and Pig. 72 represents the shell of a pond-snail. 

 In examining such a shell we see that it consists of hut 

 one piece or yalve; hence this and all 

 such shells are called "univalTes." 

 We also see that the shell is twisted 

 in a spiral, and the twists are called 

 "whorls;" the crease between any 

 two of the whorls is called the " su- 

 ture. " The first whorl forms the body 



Apex. 



Fio. 71.— Snail, Helix albolabris, (Natural size.) 



Aperture. 

 Fio. 72.— UnivalTe shell. 



of the shell, and the other smaller whorls form the "spire," 

 the end of which is called the " apex." The animal or snail 

 itself lives within the shell, but pushes its head and foot 

 but of the opening or "aperture" of the shell. The outer 

 edge of the aperture is called the lip; the inner edge is 

 thickened, and is called the " columella," which means a 

 little column. 



If we keep a land-snail in a slightly moist box or jar we 

 can observe its movements. As seen in Fig. 71, when un- 



