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 in the typical form. It is universally dis- 

 tributed. 



109. Limnasa caperata Say, pi. xxx, fig. 18. 



Limncea caperata SAY, New Harm. Diss., Vol. II, p. 230, 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, 3.00 mill. (10656.) 



10.50; " 5.00; " " 5.00; " 2.50 " (10656.) 



9.00; " 4.50; " " 4.00; " 2.50 " (10656.) 



11.00; " 5.50; " " 5.50; " 3.00 " (10437.) 



13.00; " 6.00; " " 6.00; " 3.50 " (12337.) 



15.50; " 7.00; " " 7.50; " 4.00 " (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: $|+f+|+i+|+f+f$ (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 



