THE NATURAL HISTORY SURVEY. 153 



ten ribs of somewhat unequal size. The ends of the jaw are 

 smooth on their anterior surface. 



Genitalia: "The penis sac is stout, rather short, cylindrical, 

 with a median prepuce; it receives the vas deferens at its sum- 

 mit; the retractor muscle is inserted on the vas deferens near 

 its junction with the penis sac; the genital bladder is long, 

 stout, blunt at its summit; its duct is very narrow at its entrance 

 into the bladder for a short portion of its course, then becomes 

 suddenly expanded into very much the shape and still greater 

 size of the bladder."* This peculiar arrangement of the geni- 

 tal bladder and duct distinguishes albolabris from all related 

 species. 



O ,O 



FIG. 20. 



Radula of POLYGYRA ALBOLABRIS Say. (Original.) c, central tooth; 

 1, first lateral; 12, twelfth lateral; 24,28, first marginals; 30,35, outer mar- 

 ginals; 38, abnormal marginal. 



Distribution ; Canada, Eastern and Central United States. 



Geological distribution: Pleistocene; Loess. 



Habitat: Found under and about old logs in open wood- 

 lands, and in wet weather crawling over the vegetation. 



Remarks: Distinguished by its large size, imperf orate 

 base, and white lip. This is our largest and handsomest snail, 

 and is found only in the southern and western regions. The 

 animal is slow in movement, but not at all timid, readily allow- 

 ing itself to be handled without withdrawing into its shell. 

 When crawling up the side of a glass jar the shell is so heavy 

 that it hangs almost to the extremity of the foot. The eye- 

 peduncles are pointed straight ahead during locomotion, the 

 shell is carried almost flat, and the tentacles are directed 

 straight downwards. When eating, the head is drawn partly 



*W. G. Binney, Man. Amer. Land Shells, p. 300. 



