THE NATURAL HISTORY SURVEY. 333 



about in the fluid surrounding it. Those which occurred to me 

 were found sticking to the shell of a female, although they 

 were probably not deposited by the same individual but by 

 some other, as they were huddled together in groups accord- 

 ing to their practice at this season."* ( Fig. 1 18, 2, 3). 



Radula formula : & + A + * + T*T +i+ T V+^ (3 - ' - 3) 5 

 rhachidian (central) tooth very wide, low, the ends much 

 rounded and produced, lower edge concave; center of concave 

 portion supporting a large, tongue-shaped process; ends sup- 

 porting, upon the anterior surface, four denticles, the two cen- 

 ter ones small and the outer ones larger; the ridge supporting 

 the denticles extending from the distal end of the lateral lobe 

 almost to the reflected cusp; reflection small, seven-cuspid, the 

 cusps very small except the center one, which is rather large; 



FIG. 120. 



Radula of AMNICOLA LIMOSA Say. (From nature, after Stimpson.) 

 A, central tooth; 2, 3, lateral teeth. 



intermediate tooth subquadrate, the peduncle very long and 

 somewhat enlarged at the distal end; body of tooth, at the 

 inner side, with a peculiar knob-shaped projection; reflection 

 low, wide, five-cuspid, the cusps subequal; inner cusp bluntly 

 rounded, the rest acute; lateral teeth very long and narrow, 

 the reflections small and multicuspid, the first having eighteen 

 and the second thirty cusps (Fig. 120). 



Distribution: New England to Utah and Manitoba, Hud- 

 son's Bay to Texas. 



Geological distribution: Pleistocene; Loess. 



Habitat: Found plentifully in lakes and streams, on the 

 muddy bottom, or on aquatic plants and submerged objects. 



Remarks: This abundant little species is easily recognized 

 by its globose form. The animal is very interesting in cap- 

 tivity and wanders rapidly about the aquarium with a wabbly 



