4 THE NAUTILUS. 



reduced size. The ascent of the mountain continuing, the reduction 

 in size became more pronounced, resulting in the specimens as found. 

 The shells at high altitude are less than one-half the size in any 

 dimensions, as a consequence being less than one-eighth in volume. 

 Present collecting shows that all but the two extremes have been by 

 some perchance killed, although later search may produce the inter- 

 vening specimens. But in many places in the mountains of western 

 Montana shells of medium size are found at from 5,000 feet to 6,000 

 feet or higher. 



Pyramidula sirigosa Gld., var. Cooperi W. G. B. 



This species abounds along the banks of Flathead Lake and along 

 the banks of lakes in the Mission mountains. At Sinyaleamin Lake, 

 in this range, altitude about 3,800 feet, they were not uncommon, but 

 could not be called abundant. Associated with it, but occurring in 

 very small numbers, was Polygyra townsendiana Lea, var. ptycho- 

 phora A. D. Br., and Pyramidula solitaria Say. At McDonald 

 Lake, in the same range and fifteen miles further north, the species 

 was abundant, in common again with the Polygyra and P. solitaria 

 Say. Here some two quarts were secured by a day's search among 

 the dead leaves and under decaying logs. To gather them was to 

 crawl on hands and knees among the dense growth of small trees and 

 underbrush, the interlacing dead branches being a constant hindrance 

 as well as a menace to clothing. Many live ones were secured. A 

 large series was gathered which had evidently been killed and eaten 

 by squirrels. As the pine squirrel, Sciurus richardsoni Buck, was 

 rather abundant; he is charged with the damage, though it is not 

 unlikely the little chipmunk, Taynias sp., takes a part in the work. 

 This collecting was in July, 1900. 



The shells were generally opened at the apex of the spire, a large 

 opening being made. An occasional shell was punctured at some 

 other place, but not many. The enemy seems to have discovered 

 how and where to strike in order to secure the meal with the least 

 effort. Pyramidula strigosa var. Cooperi had the larger number of 

 shells thus injured — fifty-four. Of Pyramidula solitaria fifty were 

 found cut by animals, and but three of Polygyra townsendiana var. 

 ptychophora. The two former were much more abundant, and 

 cooperi more conspicuous than solitaria. P. townsendiana were quite 

 difficult to find, and the small number of injured shells shows how 



