OF NORTH AMERICA. 



153 



is the most elongate race of stagnalis in America and were it not for 

 certain intermediate examples might easily rank as a species. 



Westerlund's subulata (Expose. Crit., 1871) is similar to wasat- 

 chensis, but has 8-9 whorls and the aperture is more oblong. In the 

 Smithsonian collection there is a peculiar form from near Fort Col- 

 ville, Washington (No. 9322) which may be regarded as an extreme 

 form of wasatchensis. The spire whorls are long and tapering, but 

 the body whorl suddenly expands to about double the diameter of the 

 penultimate whorl and is notably flat sided near the suture. A char- 



Distribution of 

 YMN^EA STAGNALIS WASATCHENSIS 



FIG. 11. 



acteristic specimen measures : Height, 42.00 ; breadth, 18.50 ; aper- 

 ture height, 19.50 ; breadth, 10.50 mill. The breadth of the last whorl 

 is 18.50 mill, while that of the preceding is but 9.00 mill. The speci- 

 mens from Fort Anderson, though far removed from the original 

 locality, seem to be good examples of the race. 



Lymnaea stagnalis lillianae (Baker). Plate XXI, figures 8-12; 

 plate XXII, figure 6. 



