THE NATURAL HISTORY SURVEY. 165 
Radula formula: 19+3+19+4+49+3+12(25—1-—25); 
central tooth with a base of attachment a trifle longer than wide, 
the outer lower corners expanded; reflection tricuspid, the 
central cusp very long, reaching to the margin of the base of 
attachment, side cusps very small; lateral teeth similar to cen- 
tral tooth, bicuspid, the inner cusp very long, the outer very 
short. The marginal teeth begin at the eleventh tooth and may 
be known by the splitting of the inner cusp; from the sixteenth 
tooth the outer cusp is split and the whole tooth becomes 
wider (Fig. 25). 
Genitalia: ‘Penis sac long, cylindrical, blunt above, where 
it receives retractor muscle and vas deferens; genital blad- 
der narrow, elongate-ovate, on a short, narrow duct; the con- 
volution in the epididymis commences near thetesticle.” (W. 
G. Binney.) 
Distribution: Canada, Eastern and Interior regions of the 
United States, Yaqui River, Guaymas, Mexico. 
Geological distribution: Pleistocene; Loess. 
Habitat: Found in damp places under fallen logs, in rot- 
ten wood, under stones, etc. 
Remarks: A species at once distinguished by its con- 
tracted aperture, notched peristome and heavy parietal tooth. 
It is one of our most abundant Helices, and in some localities 
is the predominating species. Inits movements /zrsufa resem- 
bles P. monodon. At Bowmanville it may be collected very 
abundantly in the woods just west of Lincoln Avenue. The 
species is widely distributed, being found in all the regions of 
the area. 
62. Polygyra monodon Rackett, pl. xxx, fig. 4. ; 
Helix monodon RACKETT, Linn. Trans., Vol. XIII, p. 42, pl. v, fig. 2, 
1822. 
flelix convexa CHEMNITZ, part (excl. syn. et tab. LXVI, figs. 24, 27), 
pl. x, figs. 17, 18. 
Flelix leaiti WARD MSS, teste Binney. 
Flelix cincta LEWIS, Proc. Phil. Acad., p. 162, 1874. (Variety.) 
Polygyra m2nodon alice PiLspry, The Nautilus, Vol. XI, p. 105, 1898. 
 (Variety.) 
Polygyra monodon albida WALKER, Terr. Moll. Mich., p. 15, 1899. 
(Variety.) 
Polygyra monodon friersoni PiLsBry, The Nautilus, Vol. XIII, p. 36, 
1899. (Variety.) 
Polygvra monodon imperforata PiLsBRY, Proc. Phil. Acad., p. 455, 1900. 
(Variety.) 
