430 



Till. CHICAGO ACADEMY OF SCIENCES. 



British America. 



Quebec : Chilcotts Lake, Masham, Ottawa District (Latch ford) ; Jupiter 

 River, Anticosti Island (Latchford; Macoun). 



Geological Distribution" : Pleistocene. 



RECORDS. 



Michigan: Marl beds. Crooked Lake, Oden. Emmet Co. (Slocum). 



Ecology : Appears to inhabit chiefly the large inland lakes. In 

 Owasco Lake it lives on a sandy bottom. 



Remarks : Canadensis differs from typical emarginata by having 

 a narrower and more flatly rounded body whorl, a longer, more acum- 



ns 7 e 



Fig. 48. 



inate spire, narrower and more elongated spire zi'horls, an elongated 

 instead of an ovate or rounded aperture and a more or less plicate in- 

 stead of a simple columella. The shape of the penultimate whorl is 

 very different in the two races, that of emarginata being very wide and 

 low and notably convex, while that of canadensis is high and narrow, 

 comparatively, and usually rather flatly rounded. The umbilical chink 

 is usually either absent or is reduced to a very narrow slit. In individ- 

 ual specimens it may be widely open. Typically it is a very distinct 

 race, but there are intermediate forms which show its relation to 



