pes 
ae ew 
a a o 
THE NATURAL HISTORY SURVEY. 303 
small lobe; genitalia on the left side; jaws three, thin, lateral 
plate fused with the superior jaw, ornamented with papille; 
lingual membrane broad, with numerous, crowded teeth; cen- 
tral tooth small, narrow, simple; lateral teeth broad, bicuspid, 
the inner cusp much the larger and bifid; marginal teeth ser- 
rated, longer than wide. 
Genittaha: The genitalia of Ancylus is peculiar; the ovo- 
testis is globular and the albuminiparous gland is very large, 
F 14. 103. 
Animal of ANcyLus. (After Binney.) 
tubular, and placed very near the ovotestis; the oviduct and 
vas deferens are long and the penis is very long. The figure, 
from Bronn, is sufficiently characteristic without further de- 
scription ( Fig. 104). 
Distribution: North and South America, Europe and Aus- 
tralia. 
KEY TO SPECIES OF ANCYLUS. 
fin Apex placed centrally, shell came ys: oss pe oes Seale dus wa tardus 
B. Apex placed posteriorly and directed to one side. 
a. Apex placed near the posterior end and a little to one 
side of the center. Shell depressed-conic............... rivularis 
b. Apex placed near the posterior end, at or close to the 
margin of one side. Shell very oblique.................. shimekti 
F 1G, 104, 
Genitalia of ANCYLUS FLUVIATILIS. (Bronn, Klassen und Ordnungen 
der Weichthiere, Malacozoa, taf, CIII, Fig. 16.) gh, ovotestis; gal, albu- 
miniparous gland; nb, radula sac; p, penis; rs, receptaculum seminis; 
s, salivary glands. 
122. ANCYLUS RIVULARIS Say, pl. xxx, fig. 29. 
Ancylus rivularis Say, Journ. Phil. Acad., Vol. I, p. 125, 1819. 
