LYMNMWM OF NORTH AMERICA. 399 



Range: (Figure 43). States bordering Lake Michigan. A species 

 of the Canadian region and of the humid division of the Transition 

 and Upper Austral life zones. It is apparently a species confined for 

 the most part to Lake Michigan; there is but one record (Lake 

 Geneva, Wisconsin) away from Lake Michigan and it is possible that 

 this record is due to a mixing of labels. 



RECORDS. 



Illinois : Lake shore, Ravinia, Lake Co. (Baker) ; Lake Michigan, Oak 

 Street, Chicago, Cook Co. (Lyon; Woodruff); lake shore', Lincoln Park, Chi- 

 cago (Jensen; Walcott) ; Lake Michigan, Chicago (Nason) ; Evanston, Cook 

 County (C. S. Raddin) ; Lake Michigan south of Graceland Avenue, Chicago 

 (Walcott). 



Indiana: Lake Michigan, Millers, Lake Co. (Baker; Woodruff); Lake 

 Michigan, Michigan City, La Porte Co. (Daniels). 



Michigan: New Buffalo, Berrien Co. (Daniels; Walker); High Island 

 Harbor, Charlevoix Co. (Walker). 



Wisconsin: Lake Geneva, Walworth Co. (Illinois State Laboratory). 



Geological Distribution : Unknown. 



Ecology : Woodniffi probably inhabits the deeper waters of Lake 

 Michigan as only dead shells have been found along the shore. 



Remarks : Woodniffi may be known by its very short, broad 

 spire, rapidly increasing and tumid whorls, its large, ovate or roundly 

 ovate aperture and its broad, fiat inner lip without a plait. It resembles 

 cmarginata in the form of its emarginate inner lip and catasc opium 

 in the general depressed form of the shell. The small size, large 

 aperture and peculiar inner lip will distinguish woodniffi from both of 

 these species. It somewhat resembles apicina but differs in the de- 

 pressed spire and broad, flat inner lip, without a plait. The same 

 feature will distinguish it from dccollata. The shells vary somewhat 

 in rotundity, some specimens being a trifle flattened on the body whorl 

 and having the spire somewhat elevated. The shells vary some- 

 what in the degree of umbilication which may be marked or absent. 

 The aperture may also be roundly ovate, oblong-ovate or elliptical. 

 With all this variation, however, the species seems quite distinct and 

 is very uniform in its specific features. Young shells are quite thin, 

 but adult specimens are very thick and solid and show a tendency to 

 become imperforate as well as to acquire a tubercle or swelling on the 

 middle of the columella. 



Since its discovery by Mr. F. M. Woodruff, in 1901, the species 

 has been collected in large numbers all along the southern shores of 

 Lake Michigan from Evanston, Illinois, to Michigan City, Indiana. 

 This abundance of material is ample evidence that the species is liv- 

 ing in goodly numbers somewhere in the deep water of the southern 



