THE NATURAL HISTORY SURVEY. 245 



It is quite common, but has thus far been found only in the 

 western and northern regions. The animal is very sluggish in 

 movement and does not move about like the Pupae. It varies 

 greatly in the number of teeth on the parietal wall, some hav- 

 ing one, some two, and some three teeth, the percentage of 

 each of these in a hundred being 3, 7 and 90. Specimens from 

 Riverside have two teeth, the one placed in the center of the 

 parietal wall being always the larger. When in progression 

 the shell rolls from side to side in a very peculiar manner. 



FAMILY COCHLICOPID^:. 



Shell: Elongated, polished, white or horn-colored; spire 

 turreted, aperture rounded, one-third to one-half the length of 

 the shell; columella short, arcuate to subarcuate, truncated or 

 scarcely so; peristome simple, straight, somewhat thickened 

 within. 



Animal: (See below under Cochlicopa); radula differing 

 from Achatinidae by the wide central tooth, which is narrow in 

 the latter family. 



Distribution: World wide. 



GENUS COCHLICOPA (Per.) Risso, 1826. 



Shell: Elongated, imperforate, shining, smooth, pellucid; 

 whorls rounded; aperture one-third the length of the shell; 

 columella more or less truncated; margins of peristome joined 

 by a callus. 



Animal: Foot truncated before, roundly pointed behind; 

 mantle thin; respiratory and anal orifices on right of body, 

 just beneath the peristome of the shell; generative orifice be- 

 hind the right eye-peduncle; no caudal mucus pore or locomo- 

 tive disk. 



Jaw: Long, low, wide, arcuate; ends blunt; cutting edge 

 with a single large median projection; anterior surface not 

 ribbed, but striate. Lingual membrane with central tooth long 

 and narrow, tricuspid; laterals as wide as high, bi- or tricuspid; 

 first marginals modified laterals; outer marginals wide, low, 

 multicuspid. Genitalia with a short, stout penis sac "with the 

 retractor muscle near its base; the vas deferens enters at its 

 apex, and near its entrance into the vagina it receives a curious 

 flagellate appendage, swollen below, narrow above, as long as 

 the whole system, with a large, narrowly ovate bulb at its end; 



