88 LAND AND FRESH WATER MOLLUSKS 



Range. West of the Rockies and east of the Cascade Mountains 

 on the Pacific slope. 



Oregon (Nuttall) ; Lewis or Snake River, Oregon ! Clear Lake, 

 Calif. ! In British Columbia in eastern Kootenai Lake, Lake Siniak- 

 wateen, and Osoyoos Lake ! 



As pointed out by Binney, this is quite distinguishable from any 

 form of tri-v olvts ; it differs from the true corpulentus, with which it 

 was long confounded, in its sparser and less regular axial sculpture, 

 larger and less campanulate aperture, and in the greater distance of the 

 carina from the axis. Its whorls increase more rapidly than in P. 

 traskii Lea, or even P. ammon Gould, 1 and its sculpture is markedly 

 coarser and less regular than in either of the two last cited. It is not 

 known north of British Columbia or east of the Rocky Mountains. 



FIGS. 66, 67. Planorbis btnneyt, showing animal and shell. 



Planorbis (Pierosoma) trivolvis Say. 



Planorbis tri-volvis SAY, Nicholson's Encyc., isted., n (no pagination), pi. n, 



fig. 2, 1817 ; Am. Conch., vi, pi. 54, fig. 2, 1834 (French Creek, Lake 



Erie). 

 Planorbis macrostomus WHITEAVES, 1863 (abnormal) ; + P. lentus Gould, and 



many other writers, but not of Say ; + P- tumens various California 



writers. 

 Planorbis subcrenatus CARPENTER, P. Z. S., 1856, p. 220. 



Range. The typical form belongs to the entire Atlantic drainage 

 of North America and the Mississippi Valley and northward to the 

 Etchimamish River. 



English River, Keewatin ; Lake Winnipeg, Manitoba ; Cypress 

 Hills ! Assiniboia ; Prairie Lake, Red River of the North ! ; the 

 Saskatchewan River, Laggan, Egg Lake, Red Deer, McLeod, and 

 Olds, Alberta; Lake Isle Lacrosse, Athabaska; Great Slave Lake, 

 at Fort Resolution ! and the Mackenzie River at old Fort Simp- 



1 These two species, judged by their types, which are before me, are suffi- 

 ciently distinct from any of those which have been confounded with them. In- 

 deed the true P. traskii from Kern Lake, Calif., is one of the most remarkable 

 species in our fauna. It was also found by me at Stockton, Calif., and seems to 

 have been unknown, autoptically, to Binney. 



