SHELLS OF LAKES AND STREAMS 



307 



in color and has similar habits to the last. Found 

 over most of North America. 



There are numerous other species in this family on 

 the Pacific Slope but they are only known from a few 

 localities. 



THE POND SNAILS 



(Hygro phi/a) 



This is the best represented group on the coast 

 and contains many species. All have thin horny 

 shells and differ from the Pleuroceridte and succeed- 

 ing families by breathing by lungs instead of gills 

 and by the absence of an operculum. They are 

 found in lakes and streams as well as ponds. 



The largest of this group is Lyr7i72a:a st agnails^ 

 Linne, the Pond L3'mnaea, Figure 290. This species 

 is distinguished by its long slender 

 spire and large body whorl. All the 

 members of this genus and especially 

 this species live in quiet streams or 

 lakes. Found in Eastern North 

 America, Eurasia, and the Colum- 

 bia, Klamath, Nevada, and Utah 

 Systems. 



The Marsh Lymnsea, L. palustris^ 

 Miiller, Figure 291, is one of the most 

 abundant and widespread of the pul- 

 monates. It occurs in Europe, Northern Asia and all 

 over North America from the Yukon tundras nearly 

 to Mexico. It does not occur in the Los Angeles 



