SPECIAL ANATOMY. 229 
organs, the dart sac and multifid vesicles, are so com- 
mon in European species, they are very rare in American 
species. In not one of the latter does the flagellate form 
of penis exist. A rudiment, or simplest condition of the 
multifid vesicles, only exists in four species ; H. inter- 
texta and R. gularis, in which there is a single pah- of 
follicles, and H. ligera and H. suppressa, in which there 
is but one short follicle. The dart sac exists certainly 
in only the four latter species, probably in H. berland- 
eriana, and doubtfully in H. concava. 
Bulimus. In B. fasciatus the penis is long, cylindri- 
cal, and strongly muscular. The vas deferens joins it 
near the summit ; and the retractor muscle, which is 
very long, is inserted into the latter. The oviduct is 
long, and its central part presents the peculiarity of be- 
ing colored brown. The genital bladder is ovate, situated 
near the ovary, and its duct is narrow, and as long as 
the oviduct. The vagina is broad and muscular. At 
the base of the penis, there opens a short, cylindrical 
duct, derived from a single, multifid vesicle, which pre- 
sents six or seven rounded or ovate divisions. There is 
no dart sac. 
In B. dealbatus the penis is very long ; its upper por- 
tion is narrow and very tortuous, and flagellate in appear- 
ance ; although the true flagellum, or the free portion of 
the summit of the penis beyond the insertion of the re- 
tractor muscle, is very short. The lower third of the 
penis is dilated, and presents an annular constriction ; 
vol. i. 59 
