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, pl. xxxii, fig. 12. 
Planorbts bicarinatus Say, Nich. Encycl., pl. i, fig. 4, 1817. 
Helix angulata RACKETT, Linn. Trans., Vol. XIII, p. 42, pl. v., fig. 1, 
1822. 
Planorbis engonatus CONRAD, N. Fresh Sh. Suppl., p. 8, pl. ix, fig. 8, 
1854, 
Planorbis antrosus CONRAD, Amer. Journ. Science, I ser., Vol. XXV, 
p. 343, 1834. 
Planorbis lautus H. ADAMS, Proc. Zo6l. Soc. London, p. 145, 1861. 
Planorbis bicarinatus corrugatus CURRIER, Walker, The Nautilus, Vol. 
VI, p. 186, 1893. (Variety.) 
Planorbis bicarinatus major WALKER, 1. c., p. 136, 1893. (Variety.) 
Planorbis bicarinatus var. aroostookensis PILSBRY, The Nautilus, Vol. 
VIII, p. 115, 1895. (Variety.) 
Planor bis bicarinatus striatus BAKER, |.c.,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 striz; 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, 15.00; aperture length, 6.00; width, 5.00 mill. (8487.) 
Wet eO.DUs 4) eo eeaentte ae 4.00; «3.00 (8488.) 
Ms) 5.508 noe Ons are 5.00; CO BOO of” (B486.) 
% 5.50; a 10.00; s 5.50; se A000 1 #0) (9849:) 
