GASTEROPODA OF THE UNITED STATES. 35 



at its base it is enveloped by a short prepuce. The vas 

 deferens follows the course of the penis nearly to its 

 summit. The genital bladder is oval ; its duct as long 

 as the oviduct. 



In B. virgulatus the penis is long, irregularly cylin- 

 droid, and has its base enclosed in a short prepuce. The 

 vas deferens terminates in, and the retractor muscle is 

 inserted into, its summit. The genital bladder is oval ; 

 its duct is not more than one-third the length of the ovi- 

 duct, and dilates as it passes downwards. 



In B. decoUatus the penis is short, conico-cylindroid, 

 and simple. The vas deferens enters near its base ; the 

 retractor muscle is inserted into its summit. The geni- 

 tal bladder is small ; its duct is narrow, and not longer 

 than the neck of the oviduct. 



Pupa. In P. incana the penis is short, narrow, and 

 cylindrical. The vas deferens is of a very great length 

 when compared with what it is usually in the other 

 genera. Its lower part, about the length of the penis, 

 is dilated to the size of the latter organ, is strongly mus- 

 cular, and terminates at the base of the penis. The 

 retractor muscle is inserted into the summit of the latter. 

 The lining membrane of the penis presents a single, longi- 

 tudinal fold. At the base of the penis is a short, muscu- 

 lar sac, or protuberance, probably a dart sac, although 

 the individual dissected possessed no such instrument. 

 The genital bladder is oval ; its duct is as long as the 

 oviduct, and midway receives a long, narrow duct, de- 



