THE NAUTILUS. 



this affects their mortality through foes. Being of the same color as 

 the decaying leaves and moss, and for the most part under logs and 

 debris, they seem to escape their enemies more readily than the two 

 species of Pyramidula. 



Along the banks of the Flathead Lake, near the University of 

 Montana Biological Station, this species was also found in rather 

 large numbers. In July, 1899, numbers of shells were found con- 

 taining young. While they were in colonies, yet the specimens were 

 much scattered, and it required much care and search to find them. 

 The search was usually made after a rain, which was the most suit- 

 able time for finding them, but at the same time the conditions made 

 the work very disagreeable. 



Pyramidula strigosa Gld., a small variety. 



Shells entirely difTerent from those mentioned in the preceding 

 paragraph are found on most of the low er slopes of western Montana. 

 They lit in between cooperi and alpina^ but are not found associated 

 with either variety. Nowhere does it seem abundant. The small 

 size is probably due to the shortness of the season at which the ani- 

 mals can live. By July the hills and mountain slopes have become 

 dry and parched, although in this month there are occasional light 

 showers. Their dimensions, in millimeters, are as follows for ten 

 specimens taken at .5,000 feet : Large diameter, 11.95 to 16.73, aver- 

 age 13.83; depth, 5.30 to 7.40, average 6.12 ; aperture, 4.72 to 6.67, 

 average 6.57 ; number of whorls, 4.8 to 5.4, average 6.15. 



Pyrainidida strigosa Gld., var. 



A series of shells was collected on the Tobacco Root range by Earl 

 Douglass and E. H. Murray, which the writer has examined. An- 

 other series was taken by Prin. P. M. Silloway,of Lewistown, Fergus 

 county. These are the only collections o^ strigosa made in the State 

 east of the Rocky Mountains, so far as the writer knows. They are 

 immediately recognized as differing from those west of the divide. 

 The sculpturing is coarser and they look thicker and more earthy. 

 They are decidedly greater in depth than those found on the higher 

 slopes west of the divide. They difi'er in these particulars also from 

 the high altitude form alpina. In general shape they are much like 

 cooperi, hut very much smaller. The dimensions in mm., average of 

 ten specimens, are as follows : From Tobacco Root mountains, alti- 

 tude 7,000 feet. Large diameter, 15.21 ; depth, 9.30 ; aperture, 7.06; 



