SHELLS OF LAKES AND STREAMS 311 



PL II, Fig. 2, is a very small species living on stems 

 of water plants in the Coast Range System. It is 

 elliptical, black, and has a high apex at one end. 

 A distorted second year growth has been called 

 Gundlachia calif ornica. 



Ancylus caurinus^ Cooper, PI. II, Fig. 3, is a 

 small, elliptical species living in the Columbia vSys- 

 tem. It has been confused with the last but the 

 apex is not so high and is more central; color light 

 or dark, shell glossy. 



Newberry's Keel-shell, Carinifex nciv- 

 berryi^ Lea, Figure 294, is a peculiar Plan- 

 orbis-like species related to the next. It 

 has a nearly flat spire with flat topped F'g-^a^.xi 

 whorls, keeled at the edge. The a])erture 

 is triangular and the umbilicus funnel-shaped. It 

 grows to over twice the size of the figure. Lives in 

 lakes and streams in the L^tah, Nevada, and Kla- 

 math Systems. 



The Puff -bubble, Pompholyx efjusa. Lea, PI. II, 

 Fig. 4, has a thin shell, very low spire, closed or 

 nearly closed umbilicus and is not carinate. It has 

 several doubtful varieties which are probably physi- 

 ological. Inhabits streams and lakes in the Colum- 

 bia, Klamath, Utah, and Nevada Systems. 



{Physidd^) 



The genus Physa is one of the most puzzling 

 of our shells. A great many species have been de- 

 scribed, and a number are usually recognized. The 

 writer has recently studied a large series of specimens 

 from all over the United States and has decided 



