THE NATURAL HISTORY SURVEY. 187 
cusps very short; lateral teeth (five in number) similar to cen- 
trals, but bifid, with the inner cusp the longest; marginals acu- 
leate. The cusps all have well-developed cutting points. The 
radula is similar in type to that figured under Z. arboreus. 
Distribution: Circumpolar. Northern United States and 
British America, Northern Europe and Asia. Introduced into 
the United States. 
Geological distribution: Pleistocene; Loess. 
Habitat: Same as Z. arboreus. 
Remarks: This is a neat little species, distinguished from 
its congeners by its large size, elevated spire and its rounded 
aperture. It, like arboreus, loves company, and is always found 
in little colonies. The animal is peculiar in being so very black. 
_ It is widely distributed. 
71. Zonitoides arboreus Say, pl. xxviii, fig. 9. 
Helix arborea Savy, Nich. Encycl., pl. iv, fig. 4, 1816; BINNEY’s ed., p. 
5, pl. lxxii, fig. 5. 
Flelix ottonits PFEIFFER, Olim. Weigm. Arch., Vol. I, p. 251, 1840. 
Helix brewert NEWCOMB, Proc. Cal., Acad. Sci., Vol. III, p. 118, 1864: 
flyalina viridula COCKERELL, Science Gossip, p. 257, 1889. 
Shell: Depressed, thin, umbilicated; surface shining, the 
lines of growth being so fine that the surface appears smooth 
unless examined with a powerful glass; color amber, some- 
times whitish; periphery rounded; sutures impressed; whorls 
five, regularly and evenly increasing, rounded; spire depressed, 
a trifle convex; aperture rounded,a little transverse; peristome 
simple, thin; umbilicus deep, narrow, the region indented; 
base of shell convex (see Fig. 36). 
Gr. diam., 5.00; lesser, 4.75; height, 2.75; umbilicus diam., 0.75; mill. (10095.) 
a cera Si Ose. 51M 3.00; ct 0.85; “ (10649.) 
a PO ee AN ()s ane es 2.50; 4s 0.85; “ (10096.) 
és en eeirn ered 5()= a 3.00; rf 1.00; ‘ (10098.) 
Animal: With a long, narrow, transparent foot, with 
longitudinal furrows; head, neck and eye-peduncles jet black, 
the rest of the body white and transparent except near the 
upper part, where it is bluish; eye-peduncles long and slender, 
with the eyes at their extremity; inferior tentacles very short, 
blunt; length of foot 6.00 mill.; width 0.75; pedal grooves 
and mucus pore, as usual in the genus; eye-peduncles 2 mill. 
in length (shell 5 mill. in greatest diameter). The heart is 
situated to the left of the aperture on the outer edge of the 
body-wall. The pulsations are rapid and regular; one hundred 
