296 THE CHICAGO ACADEMY OF SCIENCES. 
Habitat: Same as dbicarinatus. 
Remarks: Campanulatus is distinguished from all other 
Planorbes by its curious bell-shaped aperture. The flatness of 
the whorls will also help to distinguish it. This species, like 
' bicarinatus, is an inhabitant of rather deep water and it is diffi- 
cult to obtain alive without a dredge. It is universally dis- 
tributed throughout the area. The animal of campanulatus is 
slow in movement and the shell is carried almost perpendicular. 
In studying the last four species the writer has noted that 
there is considerable variation in the shape of the foot and 
head. Sicarinatus has a long foot and a large, rounded head, © 
both flecked with white, and the tentacles are very long and 
filiform; trivolvis has a broad, rounded, blackish foot, a wide 
head and rather short, thick tentacles; in campanulatus the foot 
is pointed behind and is very black; and in truncatus it is nar- 
rower behind than before and is of a brownish color (see 
Fig. 99). If these four species be placed side by side these 
differences may be plainly seen. 
Suscenus MENETUS H. and A. Adams, 1855. 
“Shell depressed, whorls rapidly increasing. Periphery 
angulated.” (Dall.) 
118. Planorbis exacutus Say, pl. xxvi, fig. 5. 
Planorbts exacutus Say, Jour. Phil. Acad., Vol. II, p. 165, 1821. 
Planorbis lens LEA, Trans. Amer. Phil. Soc., Vol. VI, p. 68, pl. xxiii, 
fig. 83, 1839. 
Paludina hyalina LEA, Trans. Amer. Phil. Soc., Vol. VJ, p. 17, pl. xxiii, 
fig. 81,1839. (Monstrosity.) 
Planorbis brogniartiana LEA, |. c., Vol. 1X, p. 24, 1844; Proc., Vol. II, 
p. 242, 1842. 
Planorbis lenticularis LEA, |. c., Vol. 1X, p. 6, 1844. 
Shell; Dextral, very much depressed, with an acute per- 
iphery; color pearly white; surface shining, slightly polished, 
lines of growth numerous, oblique, slightly elevated; apex dis- 
tinct, on a level with the spire; whorls four, rapidly increasing, 
sloping in a well-rounded curve to the acutely keeled per- 
iphery; spire very flat, all the whorls in the same plane, or 
very slightly depressed at the apex; sutures impressed; base 
of shell flatly convex; umbilicus rather narrow, deep, exhibit- 
ing all the volutions; aperture obliquely ovate, sometimes 
obtusely triangular; peristome thin, acute, the superior part 
produced very much over the inferior part and expanded near 
