FAMILY LYMNyEID^ 



son! (N. Lat. 62°). We have it from Moose Factory! the Slave 

 River 25 miles below Peace River ! Lake Winnipeg I the Grand 

 Rapids of the Saskatchewan River ! and hundreds 

 of more southern localities. 



The variety subcrenatzts Carpenter (Oregon, 

 Nuttall) occurs in British Columbia west of the 

 Cascades ; being, according to J. K. Lord, replaced 

 east of them by P. binncyi. We have it from 

 the Puget Sound drainage! Lake La Iloche ! 

 and Sumas Lake, B. C. ! A distorted variety 

 {dtsjectus Cooper) is reported from Lake Tahoe, 

 Calif., at a height of 6,347 feet above the sea. 

 The young shell was described from Pueblo Val- 

 ley, Oregon, by Tryon in 1S65, as P. orcgonen- 

 s/s. In 1S70 Cooper called the more common adult (but not senile) 

 form /*. occidentalis ^ and later confounded it with the Mexican P. 

 titmens Cpr., and gave it a range in California from Keni Lake, 

 Tulare Co., north to Puget Sound, and, in the coast drainage, to San 

 Francisco Baj'. There is a doubt as to whether Planorbis kornii 



Fir,. r>S. Planor- 

 15 trivolvis. 



Fig. 69. Planorbis trivolvis var. macrostomus Whiteaves. 



Tryon (1S65), from " Fort Simpson, British America," came from 

 Fort Simpson on the Mackenzie River, or Fort Simpson, British 

 Columbia ; but the figure looks more like the Pacific variety, of which 

 it is probably only a mutation. We have specimens from various 

 places in California, and Wallawalla, Wash., labelled P. Jiornii which 

 are merely a depauperate form of subcrenatus . 



On the other hand, from the Dall River, a northern affluent of the 

 Yukon in Alaska, in N. Lat. 66°, we have the typical form of trivolvis 



