THE NATURAL HISTORY SURVEY. 189 
in crevices of rotting wood, and under the bark of fallen, rot- 
ten logs. 
Remarks: This is the most common of our small land 
snails. When in progression the shell is carried on the back 
at an angle of 45 degrees, tipping to the left side of the body, 
and the head and neck are stretched far in advance of the aper- 
ture of the shell. The eye-peduncles are always nervously 
thrust about as though searching for danger, and the least 
noise or jar will cause them to be drawn into the body. Arédo- 
reus is infested by a curious parasite, Destoma appendiculata 
Leidy,* which is sometimes found in considerable numbers. 
Arboreus is more widely distributed than any other (excepting, 
perhaps, Pyramidula alternata) in this region, and there is prob- 
ably not a single locality where it is not found. It loves com- 
pany and is generally found by the dozen under the bark of 
decaying trees or under chips of wood. 
Section PSEUDOHYALINA Morse. 
Surface of shell strongly striated. 
72. Zonitoides minusculus Binney, pl. xxviii, fig. 12. 
Helix minuscula BINNEY, Bost. Journ. Nat. Hist., Vol. III, p. 435, pl. 
xxii, fig. 4, 1840. 
Flelix minutilis MORELET, nec. FERUSSAC, Test. Nov., Vol. II, p. 7. 
Flelix apex ADAMS, Contr. Conch., p. 36. 
Helix lavelleana D’ORBIGNY, Moll. Cub., in text, p. 161, excl. pl. 1853. 
Helix mauriniana D’ORBIGNY, 1. c., in pl. viii, figs. 20-22, excl. text. 1853. 
Zonites minusculus var, alachuana DALL, Proc. U.S. Nat. Mus., p.270, 
1885. (Variety.) 
Shell; Small, depressed, thin, umbilicated; surface shin- 
ing, lines of growth strong; color white, periphery! rounded; 
sutures deeply impressed; whorls four, convex, slowly and regu- 
larly increasing in size; spire almost flat, a trifle convex; aper- 
ture very nearly circular, not expanded; peristome simple, 
acute, the. basal margin rounded; terminations of aperture not 
approaching; umbilicus very large, deep, exhibiting all the vo- 
lutions to the apex; columella with a thin, testaceous deposit; 
base of shel! convex (see Fig. 36). 
Greater diameter, 1.50; lesser, 1.30; height, 0.75 mill. (10235,) 
oi. $ a oS SR et C1 A Ny ts Sa a 
Animal; With a narrow foot of medium length; eye-pe- 
duncles not very long, cylindrical; color bluish-white; mucus 
*Proc. Phil. Acad., p. 202, 1877. 
