270 THE CHICAGO ACADEMY OF SCIENCES. 
crawl over his desk like some of the land snails, which fact is 
true, in a lesser degree, of L. caperata and desidiosa. A form 
occurs at Berry Lake in which the spire is quite short, and the 
aperture longer than inthe typical form. It is universally dis- 
tributed. 
/ 
109. Limnza caperata Say, pl. xxx, fig. 18. 
Limnea caperata Say, New Harm. Diss., Vol. II, p. 280, 1829. 
Shell: Ovately elongate, rather solid, translucent; color 
yellowish horn to brown, sometimes black; surface shining or 
dull; lines of growth numerous and very fine; shell encircled 
by numerous irregular, raised spiral lines, which give the shell 
a somewhat latticed appearance; these spiral lines are placed 
on the epidermis and may be rubbed off with a brush; whorls 
five to six, convex, the last less than half the length of the shell; 
spire long, somewhat acute; sutures very heavily impressed; 
aperture ovate, its terminations more or less rounded, fre- 
quently reddish or purplish; peristome thin, sharp; columella 
strong, white, reflected so as to cover the umbilicus; there is a 
small fold crossing the center of the columella; umbilicus small, 
narrow, deep, frequently covered by the reflected columella. 
Length, 12.00; width, 5.50; aperture length, 5.50; width, 5.00 mill. (10656.) 
+; 10,80; 2%. -7:00; 3 e BOOS FN ae Be ert (10656. ) 
ra 9.00;" ~4.50; ? . 2D ic AEE Os at (10656.) 
‘e 11,003) (68 os eg # hs DO oe io ee ae (10437.) 
x 13.00; “ 6,00; ef i fl tt Pama enia es ror: | cy (12857.) 
ys D500 ey oon. ry “ Be OOS (12687.) 
Animal: Black or bluish black, lighter below and minutely 
flecked with small, whitish dots, which are scarcely visible ex- 
cept on the top of the head; head distinct; tentacles short, flat, 
triangular; foot short and wide, 8 mill. long and 3 mill. wide. 
Heart placed a trifle below the center of the columella, the 
pulsations ranging from one hundred and twenty-nine to one 
hundred and thirty-three, somewhat irregular in movement. 
Jaw: As usual. 
Radula formula: $3+3+4+4+4+44+3+43 (32—1— 32); cen- 
tral tooth as usual; lateral teeth with a subquadrate base of at- 
tachment, the reflection longer than wide and bicuspid; the 
inner cusp very large, the outer cusp short; the eighth to tenth 
teeth are modified from laterals to marginals by the bifurcation 
of the inner cusp, and the splitting up of the upper part of the 
outer cusp into small denticles; the tenth tooth is trifid on the 
