Baker — A Revision of the Limnaeas of Northern Illinois. 15 



ture roundly-ovate, more or less expanded ; peristome thin, 

 acute, sometimes expanded, in old specimens thickened by a 

 heavy deposit within; the peristome is white and there is a 

 band of very dark brown which edges the callus deposit; 

 columella oblique, reflected, with a large fold across the 

 middle, and covered by a heavy, whitish, testaceous deposit 

 which is more or less spreading; umbilicus closed by the 

 spreading callus and reflected columella, but the region is 

 indented and the umbilicus is sometimes narrowly open. 



Length 27.50 

 " 23.00 

 24.00 

 26.00 

 30 00 

 26.00 

 20.00 

 15.50 

 26.50 



it 

 « 

 tt 

 it 

 u 

 tt 

 (i 



Animal 



width 9.50 

 " 9.00 



tt 



it 



It 



<< 

 CI 

 It 

 ct 



10.00 

 13.00 

 12.00 

 12.00 

 9.00 

 7.00 

 11.00 



tt 

 tt 

 (t 

 it 

 tt 

 tt 



(9323.) 

 (8114.) 

 (9884.) 

 (8375.) 

 (8115.) 

 (8115.) 

 (9695.) 

 (9695.) 

 (9695.) 



With a short, wide foot, rounded before and 

 behind; tentacles short, triangular; color black, lighter be- 

 low, the body spotted with white which shows through the 

 shell. Heart situated as usual, pulsation regular, 80-81 per 

 minute. Length of foot 8.00, width 3.00 mills. 



Jaw : As usual. 



Radula formula: f£ + *■ + f + \+ f + i + 1^(34 — 1 — 

 34): central tooth as usual; lateral teeth of the usual type, 

 bicuspid ; tran- 

 sition teeth at 

 first like later- 

 als but tricus- 

 pid, the central 

 cusp the largest 

 (11) but soon 

 (13) the inner 

 cusps become 

 more equal and 



the outer cusp Fig. 8. Radula of Limnaea pahistris Muller. C, central 

 small • marginal tooth; 1, first lateral; 7, seventh lateral; 11-13, inter- 



, to mediate teeth ; 14-30, types of marginal teeth. 



teeth of the 



usual type (f. 8). In one membrane examined (f. 9) the first 



&&, 



