THE NATURAL HISTORY SURVEY. 165 



Radula formula: ^++^++7 +f + ^(25- I -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 the testicle." (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. In its movements hirsuta 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, pi. xxx, fig. 4. 



Helix monodon RACKETT, Linn. Trans., Vol. XIII, p. 42, pi. v, fig. 2, 



1822. 

 Helix convexa CHEMNITZ, part (excl. syn. et tab. LXVI, figs. 24, 27), 



pi. x, figs. 17, 18. 



Helix leaii WARD MSS. teste Binney. 



Helix cincta LEWIS, Proc. Phil. Acad., p. 162, 1874. (Variety.) 

 Polygyra monodon alica PILSBRY, 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.) 



