SNAILS AND MUSSELS 



and are important in the diet of frogs, fishes, and wading 

 birds. The eggs are laid in an irregular slender oval mass of 

 jelly on stones and water plants. 



Fig. 245. — Shell of pond snail, Lymncza palustris, 

 with body aperture shorter than the spire. 



Lymnaea palustris. — The shell (Fig. 245) usually has 6 

 whorls, sometimes more; it varies from pale brown to black 

 and has a white thickening (callus) on the side of the opening 

 ne.xt to the axis. Length of shell, one and one-fifth inches. 



Occurrence. — Widely distributed and in many places the 

 most common snail. 



Fig. 246. — Shell of great pond snail, Lymncea 

 stagnalis, with long spire and flattened spire whorls. * 



Great pond snail, Lymnaga stagnalis. — The shell (Fig. 246) 

 has 6 or 7 whorls, the lower ones very gradually increasing in 

 diameter so that a long slender spire is formed. Those in the 

 spire are markedly flat-sided. Length of shell, two and one- 

 half inches. The animal is horn-colored with a bluish tinge 

 on its short foot. 



The great pond snail lives in the quietest parts of ponds and 

 slow streams foraging on Elodea, Myriophyihim, and other 

 water plants or on rotting vegetation. It often travels on 

 the underside of the surface film. Some varieties live on the 

 wave-beaten shores of lakes. It lays one hundred or more 

 eggs in a single clutch. 



Occurrence. — In the northern states throughout the country. 



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