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, \\Vzarboreus, 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, pi. xxviii, fig. 9. 



Helix arborea SAY, Nich. Encycl., pi. iv, fig. 4, 1816; BINNEY'S ed., p. 



5, pi. Ixxii, fig. 5. 



Helix ottonis PFEIFFER, Olim. Weigm. Arch., Vol. I, p. 251, 1840. 

 Helix breweri NEWCOMB, Proc. Cal., Acad. Sci., Vol. Ill, p. 118, 1864. 

 Hyalina 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.) 



5.25; " 5.00; " 3.00; " 0.85; " (10649.) 



5.00; " 4.50; " 2.50; " 0.85; " (10096.) 



5.00; " 4.50; " 3.00; " 1.00; " -(10098.) 



Atiimal: With a long, narrow, transparent foot, with 

 longitudinal furrows; head, neck and eye-peduncleg 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.OO 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 



