386 THE CHICAGO ACADEMY OF SCIENCES. 
Catascopium occupies a large part of the Boreal (Canadian) and 
Transition life zones and enters the Upper Austral life zone on the 
south. In the United States it does not extend west of the humid 
division of the Transition and Upper Austral life zones. In British 
America it occupies the larger part of the Boreal (Canadian) life 
zone, east of the 115th degree of latitude and south and west of Hud- 
son Bay, extending south into North Dakota. Its northern limit seems 
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i 
Distribution of 
CATASCOPIUM 

Fic. 45. 
to be Great Slave Lake at about the 60th parallel. It probably in- 
habits some of the country to the east of Hudson Bay, but no speci- 
mens or authentic records have been seen; Dall reports it from Ungava 
and Labrador. Its center of distribution appears to be the Great 
Lake region lying to the southwest of Hudson Bay. It has not been 
found in the great plains area, but is common in the prairie regions 
of the central west. It is a common mollusk in the Canadian, Hud- 
