Trans. Acad. Sci. of St. Louis. 



Radula formula: ^| + i + f + i+i + i+H(35--l 

 — 35): central tooth as in the genus; lateral teeth with a 

 quadrate base of attachment; reflection long and rather wide, 

 reaching below the base of attachment, bicuspid, the inner 

 cusp very large and long, the outer cusp small and sharp; the 

 tenth tooth is trifid and connects the lateral and marginal 

 teeth ; marginal teeth much longer than wide, generally four- 

 cuspid, the inner cusp placed 

 about midway of the reflection, 

 the other three placed at the dis- 

 tal end ; there are generally sev- 

 eral small denticles on the upper 

 inner edge of the reflection; the 

 outer marginals have all the cusps 

 placed at the distal end and the 

 margins are simple {f. 2). 



Distributio7i : New England to 

 Iowa, Canada to Georgia; Tepic, 

 New Mexico.* 



Geological Distribution : Pleis- 

 tocene ; Loess. 



Habitat: Found abundantly in 

 small ponds and creeks where the 



3f 



IS > 

 Fig. 2. Radula of Limnaea colu- 

 mella Say. C, central tooth ; 1, 

 first lateral; 10, first marginal; 



water is more or less stagnant. 



25, 30, 35, typical outer margi- 

 nals. 



Particularly fond of a locality 

 where lily pads are in abundance. 

 Remarks: This species is very 

 variable in the shape of its aperture, and several distinct 

 species have been made from these variations, which will 

 stand simply as varieties. It is very frequently taken for 

 JSuccinea and the shell bears a very strong resemblance to 

 that genus. The animal, however, is quite diJfferent, and 

 shows that it is a genuine Limnaea. The raised spiral lines 

 are very beautiful, and different from those of any other 

 Limnaea in our area. So far as known it has only been col- 

 lected in the greenhouse and lily ponds in Lincoln Park. 



* Vide J. G. Cooper, Proc. Cal. Acad. Sci. ii. 51 : 167. 1895. 



