FAMILY 



8 9 



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

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

 Rapids of the Saskatchewan River ! and hundreds 

 of more southern localities. 



The variety subcrenatus Carpenter (Oregon, 

 Nuttall) occurs in British Columbia west of the 

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

 east of them by P. binneyi. W r e have it from 

 the Puget Sound drainage ! Lake La Hoche ! 

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

 {disjectus Cooper) is reported from Lake Tahoe, 

 Calif., at a height of 6,247 f eet above the sea. 



T7* /"Q ~DJ 



The young shell was described from Pueblo Val- 



' . bis tnvolvis. 



ley, Oregon, by Tryon in 1865, as P. oregonen- 

 sis. In 1870 Cooper called the more common adult (but not senile) 

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

 tumens Cpr., and gave it a range in California from Kern Lake, 

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

 Francisco Bay. There is a doubt as to whether Planorbis hornii 



FIG. 69. Planorbis trivolvis var. macrostomus Whiteaves. 



Tryon (1865), 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. hornii 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 



