292 THE CHICAGO ACADEMY OF SCIENCES. 



in movement and carries its shell at an angle of 45. While 

 watching this species (as well as others) feeding upon the 

 glass sides of a jar, it seems evident that the entire radula is 

 exserted when eating the growths on the glass, in exactly the 

 same manner that a cat laps up milk. While feeding, the su- 

 perior jaw may be plainly seen, as well as the radula. 

 116. Planorbis bicarinatus Say, pi. xxxii, fig. 12. 



Planorbis bicarinatus SAY, Nich. Encycl., pi. i, fig. 4, 1817. 



Helix angulata RACKETT, Linn. Trans., Vol. XIII, p. 42, pi. v., fig. 1, 

 1822. 



Planorbis engonatus CONRAD, N. Fresh Sh. Suppl., p. 8, pi. ix, fig. 8, 

 1834. 



Planorbis antrosus CONRAD, Amer. Journ. Science, I ser., Vol. XXV, 

 p. 343, 1834. 



Planorbis lautus H. ADAMS, Proc. Zool. Soc. London, p. 145, 1861. 



Planorbis bicarinatus corrugatus CURRIER, Walker, The Nautilus, Vol. 

 VI, p. 136, 1893. (Variety.) 



Planorbis bicarinatus major WALKER, 1. c., p. 136, 1893. (Variety.) 



Planorbis bicarinatus var. aroostookemis PILSBRY, The Nautilus, Vol. 

 VIII, p. 115, 1895. (Variety.) 



Planorbis bicarinatus striatus BAKER, I.e., Vol. XV, p. 120, 1902. (Variety.) 

 Shell: Sinistral, discoidal, angulated; color yellowish or 

 brownish horn, sometimes dark brown or reddish; surface shin- 

 ing, lines of growth oblique, numerous, strong elevated, crossed 

 by very minute striae; apex small, but visible at the base of 

 the cone-shaped depression formed by the spire; whorls three, 

 discoidal, sharply carinated above and below; periphery 

 rounded; spire exhibiting all of the volutions but forming a 

 cone-shaped depression; sutures impressed; base of shell form- 

 ing a deep umbilical depression which exhibits all of the volu- 

 tions; aperture lunately-ovate, rounded below and v-shaped 

 above, where it rises far above the body whorl; the aperture 

 (usually) forms a slight bell-shaped enlargement, higher than 

 wide; peristome thin, acute, expanded, thickened within by a 

 bluish-white callus, and with a band of reddish-brown just back 

 of this; extending from the termination above to the v-shaped 

 depression below; terminations connected by a thin callus; in- 

 terior of aperture whitish or brownish; sometimes there are 

 two whitish spiral bands within the aperture, where the superior 

 and inferior carinations make a shoulder, and extend far within 

 the throat. 

 Length, 6.50; width, 13.00; aperture length, 6.00; width, 5.00 mill. (8487.) 



" 5.50; " 9.00; " 4.00; " 3.00- " (8488.) 



" 5.50; " 10.50; " 5.00; " 3.50 " (8486.) 



" 5.50; " 10.00; " 5.50; " 4.00 " (9349.) 



