Baker — A Revision of the Limnaeas of Northern Illinois. 23 



the teeth. The number of teeth seems to vary in different 



individuals; the writer has counted from 46 — 1 — 46 to 54 — 



1 — 54; Binney (L. 



&F.W. Sh.,p. 28) 



gives 40 — 1 — 40 



and (p. 155) 47— 



1_47 teeth; Bland 



and Binney (Am. 



Journ. Conch. 7 : 



161) give 40—1— 



40. It is probable 



that the membrane 



having 54 — 1 — 54 



teeth was abnormal . 



46 — 1 — 46 is the 



number generally 



counted by the 



writer (f. 13). 



Distribution : 

 North America, 

 Europe, Asia; cir- 

 cumpolar. 



Fig. 13. Radula of Limnaea stagnalis Linne\ C, 

 central tooth, abnormal; 1, first literal; 2, 

 second lateral; 14, fourteenth lateral or first 

 intermediate; 19, 23, marginal teeth. 



Geological Distribution ; Pleistocene; Loess. 



Habitat: Found generally in stagnant spots of ponds and 

 rivers about decaying vegetation. Rotting fruit or vegetables 

 floating in the water will be found a good habitat for this 

 species. Dredged from a depth of ten meters at High Island 

 Harbor, Lake Michigan (vide Bryant Walker). 



Remarks: This is our largest and finest Limnaea, easily 

 distinguished by its large size, pointed spire and ample 

 aperture. It varies to a great extent, principally in the form 

 and size of the aperture, which is normally about the same 

 length as the spire, but may be twice its length ; it may also 

 be elongately rounded or spreading and flaring. With all its 

 variation, however, it is easily identified and cannot be mis- 

 taken for any other shell. This species may be classed with 

 palustris, under the remarks on the latter species, in regard 

 to its food. It has been seen about dead carcasses of a 

 number of animals. 



