172 THE CHICAGO ACADEMY OF SCIENCES 
64. Circinaria concava Say, pl. xxviii, fig. 4. 
Flelixiconcava SAY, Journ. Phil. Acad., Vol. II, p. 159, 1821. 
Helix planorboides F ERUSSAC, Hist. Nat. Des. Moll., pl. 1xxxii, fig. 4. 
Helix dissidens DESHAYES, in FERUSSAC, Hist. Nat. Des. Moll., Vol. I, 
p. 97, pl. Ixxxiv, figs. 1, 2. 
Shell: Depressed, rounded, almost flat on the upper sur- 
face; color light yellowish-horn, withatinge of greenish; sur- 
face shining, covered with numerous crowded, raised lines of 
growth; whorls five, rounded below, flat above, the outer whorl 
somewhat spreading as it approaches the aperture; spire flat 
or only slightly convex; sutures very deeply excavated as they 
approach the aperture; aperture rounded-oblique, flattened 
above by a deflection of the peristome; the aperture is fre- 
quently tinged with brownish; peristome flattened and de- 
flected above its junction with the last whorl, the portion near 
the columella subreflected; columella witha rather thin callus, 
which connects the two extremes of the peristome; umbilicus 
wide, deep, spreading, showing all the volutions to the apex; 
base of shell rounded. 
Greater diameter, 15.00; lesser, 12.50; height, 6.50; umbilicus, 5.00 mill. 
(10094.) 
Greater|diameter, 14.00; lesser, 12.00; height, 6.50; umbilicus, 4.50 mill. 
(7766.) 
Animal; (Fig.29.) With a narrow body; anterior portion 
much in advance of shell; color blackish, mottled with light 
FiG. 29. 
Animal of{CIRCINARIA CONCAVA Say. (After Binney.) 
horn; eye-peduncles long, cylindrical, bluish, eyes at tip, on 
rounded protuberances; tentacles comparatively long and slen- 
der, cylindrical; foot obtusely rounded behind, blunt before; 
creeping disk long andrather broad; head prominent; respira- 
tory orifice on right side just beneath a point where the per- 
istome meets the body of the last whorl; contractions of foot 
strongly marked when viewed through a glass; base of animal 
dirty white; collar reddish-orange. Length of foot 14.25 mill., 
with 4.00 mill. 
The heart is situated 5 mill. from the edge of the aper- 
ture, and is very plainly seen through the transparent shell, 
