CHAPTER IX. 



SNAILS AND OTHER UNIVALVE SHELL FISH. 



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

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

 Our common large land-snail is called Helix albolabris 

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

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

 one piece or valve; hence this and all 

 such shells are called " univalves." 

 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 



FIG. 71. Snail, Helix albolabris. (Natural size.) 



Aperture. 



FIG. 72. Univalve shell. 



"spire/' 



of the shell, and the other smaller whorls form the 

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

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

 out 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- 



