Bul. Univ. of Mont., Biol. Series No. 3. Plate XNVII. 
A series of shells showing the varieties of Pyramidula Strigosa due to high altitude. 
The largest, to the left, from McDonald Lake, altitude 3300 feet. The next size, from 
Tobacco Root Mountains, east of the mainrange. The third, from the Bitter Root Moun- 
tains, altitude 5000 feet. The smallest, from McDonald Peak, altitude 8000 feet. Photo 
by M. J. E. 
