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 

 f 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; width 2 75 mill. 



6.00; 



6.75; 

 11.25; 

 14.00; 



4.00; 

 4.00; 

 6.50; 

 6.00; 



3.50; 

 4.00; 

 6.50; 

 7.00; 



2 00 

 2.00 

 3.50 

 3.50 



(10655.) 

 (10655.) 

 (10492.) 

 (12475.) 

 (12686.) 



Animal; Similar to that of caperata. 

 Jaw; As usual, striated. 

 Iiadula formula : 



114.24.i-Li _L.JL4-A4-i4-2.4- _2_. 

 (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 



(/• 7). 



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 Fir.* 



f 



Fig. 7. Radula 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. 



