Baker — A Revision of the Limnaeas of Northern Illinois. 13 



vex, the last whorl inflated, occupying from one half to three 



fifths of the total length of the shell; spire short, obtuse, 



conic; sutures much impressed; aperture roundly ovate, % to 



4 the length of the shell, the terminations rounded; peristome 



thin, sharp, thickened inside by a reddish deposit; columella 



strong, reflected over the narrowly open umbilicus ; columella 



with a small fold. 



Length 10.00; width 5.00; aperture length 5.50 



" 6.00; " 4.00; " " 3.50 



«■ 6.75; < ; 4.00; " " 4.00 



" 11.25; " 6.50; " " 6.50 



" 14.00; « 6.00; " " 7.00 



Animal: Similar to that of caperata. 



Jaw: As usual, striated. 



Radula formula: !t + ! + Hl +t+I + i+!+ ^ 

 (30 — 1 — 30): central tooth as usual; first four laterals 

 with a quadrate base of attachment, about as wide as high ; 

 reflection bicuspid, the inner cusp very large, the outer cusp 

 smaller; fifth to seventh transitory, the inner cusp becom- 

 ing split up into two cusps and a smaller cusp appearing on 

 the outer side of the outer cusp ; 

 eighth, and all after true margi- 

 nals, long and narrow, with from 

 five to seven cusps ; at first two 

 of the cusps are situated some 

 distance up the outer margin of 

 the cusp; but finally (20) they 

 appear only on the distal end 



Distribution : New England to 

 California, Michigan and Dakota 

 to Texas and Mexico ; Cuba. 



Geological Distribution: Pleis- 

 tocene ; Loess. 



Habitat: Similar to and almost 

 always associated with caperata. 



Remarks: This species, long known as umbilicata, has 

 been shown by Mr. Pilsbry to be a synonym of cubensis Pfr.* 



Fig. 7. Kadula of Limnaea cuben- 

 sis Pfr. C, central tooth; 1-4, 

 first lateral teeth; 5, 6, 7, tran- 

 sition teeth; 8, 9, 12, 20, mar- 

 ginal teeth. 



* Vide Proc. Phil. Acad. 1891 : 321. 



