258 MANUAT OF THE MOLLUSCA. 
viviparous; the shells of the young are ornamented with spiral 
rows of epidermal cirri. 
Distribution, 60 species. Rivers and lakes throughout the 
northern hemisphere ; Black Sea, Caspian. 
Fossil, 53 species. Wealden—. Britain, &c. 
Sub-genus.  Bithynia (Prideaux), Gray. 3B. tentaculata 
(Pl. IX., Fig. 27). Shell small; operculum shelly. Animal 
oyiparous; with only one neck-lappet, on the right side. The 
bithynia oviposit on stones and aquatic plants; the female lays 
from 30 to 70 eggs in a band of three rows, cleaning the surface 
as she proceeds; the young are hatched in three or four weeks, 
and attain their full growth in the second year. (Bouchard.) 
- 
AMPULLARIA, Lam. Apple-snail, or idol-shell. 
Litymology, anvpulla, a globular flask. 
Example, A. globosa (Pl. TX., Fig. 30). 
Synonym, Pachylabra, Sw. 
Shell globular, with a small spire, and a large yentricose body- 
whorl; peristome thickened and slightly reflected ; operculum 
shelly. 
Animal with a long incurrent siphon, formed by the left neck- 
Fig. 109.* 
Jappet; left gill developed, but much smaller than the right ;t+ 
muzzle produced into two long tentacular processes; tentacles 
* Fig. 109. Ampuilaria canaliculata, Lam. (from D’Orb). South America. The 
branchial siphon (s) is seen projecting from the left side; 0, operculum, 
{ The ampullaria is said to have a pulmonic sac in addition to its gills (Gray, Owen), 
but we have not met with specimens. sufficiently well preserved to exhibit it. It would 
be very desirable to examine the amp. cornu-arietis, in which, probably, the gills are 
symmetrical, as in the ceplialopods. 
