SHELLS OF LAKES AND STREAMS 315 



small o and has a more elevated spire than the pre- 

 ceding; sutures impressed. It lives in springs, lakes 

 and mountain streams in the Klamath, Nevada, 

 Utah, Coast Range, Los Angeles and x^rizona Sys- 

 tems. P. stearnsiaria and imitator are identical. 

 They were founded on live specimens while P. lon- 

 (jinqua was described trom bleached specimens from 

 the Colorado Desert, possibly distorted by alkali 

 waters. 



Faludestrina protea, Gould, the Variable Palu- 

 destrina, PL III, Figs. 14 and 15, is well named. 

 It is about the same size but always more slender 

 than the last, sometimes attenuate. It is normally 

 smooth, but forms from alkaline springs and Jakes 

 are often spirally ridged, vertically plaited or both. 

 On the Colorado Desert in Southern California, the 

 white bleached shells of this species blow before the 

 wind in countless millions. In former times this 

 desert was the bed of a large lake. The species must 

 have swarmed in it. Found in lakes and hot springs 

 in the Utah, Nevada, and Arizona Systems, also 

 Mexico and New Mexico. 



The Tawny Flood-shell, Fluminicola 

 fusca^ Hald., Figure 298, is about the size 

 of a pea. It has a short spire and the 

 shell is quite solid and a dark bluish black. Fig. 298 

 Found in streams in the Utah System. 



Fluminicola seminaUs^ Hinds, the Brown Flood- 

 shell, PI. Ill, Fig. 12, is a thinner green-brown spe- 

 cies found in similar situations in the Klamath 

 System. It has a more elevated spire. 



Figure 299 represents Fluminicola nuttalliana^ 



