182 THE CHICAGO ACADEMY OF SCIENCES. 
when viewed from the aperture. As in Z. avboreus the head 
and neck are carried far in advance of the shell, when in mo- 
tion. This is also acommon species, although not as numer- 
ous in individuals as 7. arboreus. It seems to occupy about the 
same localities as that species. 
SecTion GLYPHYALINIA Martens, 1892. 
68. Vitrea indentata Say, pl. xxviii, fig, 11. 
Helix indentata SAy, Journ. Phil. Acad., Vol. IJ, p. 372, 1822. 
Hyalinia subrupicola DALL, Bull. U. S. Geol. and Geogr. Surv. of Terr., 
Vol. III, p. 163, 1879. 
Zonttes indentatus var. umbilicatus SINGLEY, British Naturalist, April, 
1893, p. 81. 
Shell: Small, depressed, thin, pellucid, subperforated, fre- 
quently almost imperforate; surface shining, polished, covered 
with strong, impressed striz which are equidistant, the spaces 
on the last whorl being much wider than the striz; color, yel- 
lowish or dark horn; periphery rounded; sutures impressed; 
whorls four and one-half, rapidly increasing, the outer whorl rap- 
ie Ge 
FG. 38. 
Jaw of VITREA INDENTATA Say. (Original.) 
idly enlarging as it approaches the aperture; spire flat, a little 
convex; aperture large, transversely oval; peristome simple, 
thin, acute, the lower portion extending clear to the umbilicus; 
umbilicus not perforated, but the region is strongly indented; 
base of shell convex (Fig. 36).* 
Greater diameter, 5.00; lesser, 4.50; height, 2.50 mill. (10221.) 
P = 5.00; “ 4,50; opt hs BS (10222.) 
Animal: Similar to Z. avboreus and V. hammonis; black- 
ish above, lighter below and on the sides; foot g mill. long, 
2 mill. wide, shell 5 mill., greater diameter. Heart as in the 
other species of the genus, puisations regular, 160-162 beats 
per minute. When the animal is emerging from the shell the 
heart almost stops beating. 
Faw: Long, narrow, somewhat bow-shaped, ends bluntly 
pointed; upper margin rounded, lower margin with a broad, 
median projection (Fig. 38). 
*These figures are introduced to enable the student to perceive the differences between 
these minute shells. 
