290 



THE CHICAGO ACADEMY OF SCIENCES. 



RANGE (Figure 31) : Maine west to Wisconsin, northern Michi- 

 gan south to northern Illinois. 



This variety occupies a large part of the Alleghanian division of 

 the Transition life zone ; it enters the Carolinian division of the Upper 

 Austral life zone on the south and the Boreal (Canadian) life zone 

 on the north. This area of distribution will probably be greatly ex- 

 tended when the variety becomes known. It has been confounded with 

 obrussa heretofore. The geological range is at present much wider 

 than the present range (the race has not been observed living outside 

 of Illinois and Michigan), probably showing that the variety is ap- 



Distribution of 

 DEGAMP1 

 Geological 

 bed? 

 Other Post-Glacial Deposits. 



FIG. 31. 



preaching extinction. As a marl fossil it is one of the most abundant 

 of the Lymnseas, and a characteristic mollusk of the Canadian and 

 Nova Scotian regions. 



RECORDS. 



UNITED STATES. 



ILLINOIS: Fox Lake, Lake Co. (Baker) ; Silver Lake and Algonquin, Mc- 

 Henry Co. (Nason) ; Cedar Lake and Long Lake, Lake Co. (State Laboratory). 



MICHIGAN: Brook's Lake, Newaygo Co. (Streng; Walker); Charlevoix, 

 Hillsdale, Jackson, Lake, Marquette, Muskegon, Newaygo, Shiawassee and Tus- 

 cola Counties (Walker 1 ). 



GEOLOGICAL DISTRIBUTION : Pleistocene. 



1 A number of these records refer to fossil or subfossil specimens. 



