190 THE CHICAGO ACADEMY OF SCIENCES. 



pore placed on the upper surface of the extremity of the foot; 

 pedal grooves distinct. 



Jaw: Similar in shape to that of Vitrea indentata, with a 

 broad, inconspicuous median projection (see Fig. 38). 



Radula formula: f +|+f +i+f+ir+H"-i-i2); teeth 

 similar in form to those of arboreus, excepting that they are a 

 little wider; the fourth lateral is modified. There are over 50 

 rows of teeth. 



Distribution: "Ontario to Florida, west to Montana, Ari- 

 zona and New Mexico, Bermuda." (Pilsbry.) West Indies, 

 Japan. (Binney.) Manitoba. (Hanham.) 



Geological distribution : Pleistocene; Loess. 



Habitat: Found in and about rotting logs in damp woods. 



Remarks: A common species, distinguished by its small 

 size, flattened spire and very wide umbilicus. The animal is 

 very timid in captivity, hesitating a longtime before starting 

 to crawl over the surface upon which it has been placed. Like 

 the Vitreas which it somewhat resembles, this little species is 

 widely distributed, and will ultimately be found to be as com- 

 mon as Z. arboreus, when all parts of the area are thoroughly 

 explored. 



GENUS QASTRODONTA Albers. 



Gastrodonta ALBERS, Die Helicien, p. 88; Malak. Blatter, Vol. IV, p. 



91, 1857. 

 Ventridens BINNEY & BLAND, Land and Fr. Wat. Shells, N. A., Part I, 



p. 292, 1869. 



Shell: Usually umbilicated, rather thin; horn-colored, 

 glassy, covered with coarse striae; whorls five to seven; aper- 

 ture lunate, exhibiting two modifications: (i) with teeth or lam- 

 inae on the base (gularis Say); (2) with a strong white callus 

 on the floor of the last whorl (ligera Say); peristome simple, 

 acute. 



Animal: Generally blackish; head, neck and eye-pedun- 

 cles much darker, the latter very long; mucus pore a longi- 

 tudinal furrow, situated on the upper surface of the extremity 

 of the foot, and opened and closed at will. Locomotive disk 

 furrowed above the margin of the foot. Genitalia provided 

 with a dart sac, in which is contained a long, curved, calcareous 

 dart upon the vagina.* 



*Pilsbry, Proc. Phil. Acad., 1894, p. 16. 



