158 THE CHICAGO ACADEMY OF SCIENCES. 
Genitalia: ‘‘The penis sac is short, stout, cylindrical, re- 
ceiving the vas deferens and retractor muscle at its summit; 
the genital bladder is small, elongated, bluntly tapering at its 
apex, on a short, narrow duct; the oviduct is greatly convo- 
luted.” (W. G. Binney, I. c.) 
Distribution: Canada to Minnesota, south to St. Simons 
Islands, Georgia, and Texas. (Pilsbry.) 
Geological distribution: Pleistocene; Loess. 
Habitat: Found under rotten logs and pieces of wood in 
forests where there is more or less moisture, particularly near 
the edge of the woods. On rainy days or just after a rain, it 
may be seen crawling over the ground, on tree trunks, etc. 
Remarks: Thyroides is distinguished from all others of the 
group by its open umbilicus, thin, spreading peristome and 
wide aperture. The parietal tooth is frequently wanting, and 
a variety of the ducculenta form is imperforate. In habits the 
animal varies, some specimens being shy in captivity and re- 
quiring a great amount of persuasion to induce them to crawl 
over the hand or on a table; other individuals are bold and 
will readily crawl over the extended hand, and will even allow 
themselves to be picked up by the shell without withdrawing 
into it. It is found in all parts of the area. 
58. Polygyra clausa Say, pl. xxix, fig. 4. 
flelix clausa SAY, Journ, Phil. Acad., Vol. II, p. 154, 1821. 
Helix ingalisiana SHUTTLEWORTH, Fischer's Notitiz, Vol. II, pl. iii, 
fig. 5. 
Shell: Semi-globose, varying from thin to rather solid, 
umbilicated; surface with very numerous crowded, oblique, 
rib-like lines of growth, crossed by numerous fine spiral lines; 
the nuclear whorl is smooth; color yellowish to greenish-horn; 
periphery broadly rounded, sutures deeply impressed; whorls 
five to five and one-half, rounded, convex, rather closely and 
regularly increasing, the last a little spreading; spire varying 
from somewhat depressed to elevated and sub-conical; aperture 
diagonally lunate, expanded above, narrowed below, the colu- 
mella a trifle dilated; peristome contracted behind the narrowly 
reflected portion, which is white and rounded in old specimens; 
the terminations widely separated and connected by a very thin 
callus; umbilicus of good size, partly covered by the reflected 
columellar portion of the peristome; base of shell rounded. 
Greater diameter, 17.00; lesser, 15.00; height, 10.50; mill. (11910,) 
y: a 18.00; domain IK 0 1 “12,003 "8s (1 2406") 
