244 THE CHICAGO ACADEMY OF SCIENCES. 



foot; the base of the foot is whitish; length of the foot 2.00 

 mill., width i.oo mill. 



Jaw: Very much arched, the ends square and the whole 

 length very uniform in width; the concave portion bears a very 

 well-developed median projection; the anterior surface is lon- 

 gitudinally striated (Fig. 73, J). 



Radula formula: VH +f + i+f+f +A ( 14-1-14); 

 central tooth with a base of attachment a little longer than 

 wide; almost rectangular, with a broad reflection which bears 

 the short cusps, rather stout, of which the center cusp is the 

 longest; the lateral teeth (6) are similar but asymmetrical, 



Fig. 73. 



Radula of VERTIGO OVATA Say. (Original.) c, central tooth; 1, first 

 lateral; 5, fifth lateral, modified; 11, typical marginal; J, jaw. 



tricuspid, the inner cusp being large and the two outer cusps 

 small, the inner cusp reaching half way to the lower border of 

 the base of attachment; the outer laterals (3) are somewhat 

 modified, the inner cusp becoming shorter; the marginal teeth 

 (5) are low and wide and serrated, the inner cusp being quite 

 large and the outer cusps (3-5) being quite small. There are 

 about 90 rows of teeth (Fig. 73). 



Genitalia: Unknown. 



Distribution: North America and parts of Europe. 



Geological distribution : Pleistocene. 



Habitat: Found rather plentifully under sticks, stones, 

 leaves, etc., in moist places, especially along the banks of riv- 

 ers, ponds and creeks. 



Remarks: This species is at once distinguished by its 

 dentate aperture and the peculiar constriction of the last whorl. 

 Zonites upsoni Calkins is probably nothing but the young of this 

 species. Most, or all, of the Pupae are very small when young. 



