308 WEST COAST SHELLS 



or Arizona System but is found in all the 

 others. It is rather variable but can usu- 

 ally be easily recognized. It is large, with 

 the length of the aperture about equal to 

 the height ot the spire, which is not so 

 slender as that of L. stagnalis. The shell 

 is often marked b}- tine spiral lines and 

 Fi^29i again by malleations giving it an appear- 

 ance of mosaic. It is dark horn-color. 

 hymn(£a ohrussa. Say, the Narrow-mouth Lym- 

 nsea, PI. Ill, Fig. 7, resembles small specimens of 

 the last but has a narrower aperture, thinner shell 

 and lacks the spiral lines. It is found on confervse 

 in rapid streams, ponds and often in merely moist 

 places, in the United States and southern Canada. 

 On the west coast it occurs as far south as the Colo- 

 rado, Utah, Nevada, and Coast Range Systems. 



hymn^za cubensis, Pfeiffer, the Cuban Lymnsea, 

 PI. Ill, Fig. 4, and its several varieties are among 

 our most common shells, but are usually overlooked 

 as they are seldom found in the water, but usually 

 near it or on floating algae. They have a straight 

 reflexed pillar; some are stubb}^ and some are slen- 

 der; some have a nearh^ closed umbilicus and some 

 a wide open one. The following table will perhaps 

 explain their relations better than a lengthy descrip- 

 tion. In general the forms with an open umbilicus 

 are not found north of the Coast Range System, 

 while the forms with a closed umbilicus do not 

 range south of it. Inhabits the Antilles, Florida, 

 Mexico, and nearly the whole United States west 

 of the Mississippi River, rephicing Lyinnc^a capcrata 

 of the Eastern States. 



