LYMNA:IDA OF NORTH AMERICA. 309 
Lakes and the Rocky Mountains. Its route of dispersal in Post-Glacial 
Time is plainly indicated on the map, via the ancient waterways con- 
nected with Lake Agassiz, Lake Warren and Lake Chicago. -A small 
colony doubtless found refuge in Alaska during the Ice Age, and was 
subsequently scattered over the northwestern portion of British Amer- 
ica via the Yukon River. 
GEOLOGICAL RANGE (Figure 34): Pleistocene. Palustris has been 
found in various Pleistocene and recent deposits. It is rare in the 
Leess, but very common in certain sand, gravel and lacustrine de- 
posits. Call mentions it as an abundant post-Lahontan fossil ranging 
downward to the Middle Lahontan, Nevada. It is abundantly dis- 
tributed throughout the Bonneville area in Utah. In the inter-glacial 

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deposits of the Don Valley, near Toronto, and in those of the western 
shore of Cayuga Lake, in New York, it is also abundant. Geograph- 
ically the geological range is from New Brunswick to California, 
forming a belt about ten degrees in width. The Missouri, and espe- 
cially the Texas and Arizona records, indicate that the species for- 
merly ranged well into the Lower Mississippian region. No recent 
specimens have been seen from Texas, and the descriptions of the 
deposits lead to the opinion that they are of considerable antiquity, 
perhaps pre-glacial. 
RECORDS. 
UNITED STATES. 
LESS. 
Iowa: Division Street, Davenport, Scott Co., near the base of the Leess 
(Leverett; Shimek; Udden). 
