248 THE CHICAGO ACADEMY OF SCIENCES. 



one's hand. In progression it is very rapid, probably exceed- 

 ing, in comparison with its size, all other species in the rapidity 

 with which it crawls. It seems to be confined to the northern 

 and southern regions. 



FAMILY VALLONIID^E .* 



For general characters of the family, see the description 

 of the genus Vallonia, below. 



GENUS VALLONIA Risso, 1826. 



Shell: "Minute, openly and widely umbilicate, depressed, 

 the spire low-convex, consisting of 3 to 4^ whorls, color light 

 and uniform; surface smooth or ribbed; periphery rounded; 

 last whorl usually descending in front. Aperture oblique, circu- 

 lar or short-oval; peristome continuous or nearly so, expanded 

 or reflexed, often thickened within." (Pilsbry.) 



Fig. 76. 



Genitalia of VALLONIA PULCHELLA Miiller. (Pilsbry, Guide to Heli- 

 ces, pi. Ixiii, Fig. 9.) 



Animal: "Foot small, short, with no pedal grooves; edges 

 of sole somewhat crenulated; sole undivided; eye-peduncles 

 cylindrical, not enlarged distally; tentacles short; labial lobes 

 well developed. Genitalia (Fig. 76) having the penis short, 

 with terminal retractor; epiphallus short, bearing a flagellum. 

 Dart sack present, single, containing a straight, bladeless dart. 

 No mucus glands. Duct of spermatheca long, branchless." 

 (Pilsbry). For jaw and radula see V. pulchella. 



Distribution: "North America south to Texas; Japan and 

 middle China to Europe and Atlantic Islands." (Pilsbry.) 

 Found fossil in the Eocene and Miocene. 



The position of this family, as well as that of Cochlicipidse, is very uncertain, and it is 

 placed here provisionally. 



