BITHINIA. 
25 
inner surface of the respiratory cavity: the 
ridges narrow, slightly dilated, and angulated 
near the middle. {Moquin Tandon^ t. 39. f. 31. 
32.) Stomach with cartilaginous stylets. Male 
organs at the hinder base of the right tentacle, 
always exposed, filiform, bifid. {Moquin Tan- 
don^ t. 39. f. 37.) Shell spiral; mouth oval, 
entire; peristome thickened. Operculum an- 
nular, with an internal shelly coat; crabby 
claws, not withdrawn in the aperture of the 
shell. Oviparous, eggs in oblong masses. 
1. Bithinia Gray. (Bithinia.) 
Operculum filling the mouth of the shell, lined 
internally with a thick shelly coat ; nucleus 
subcentral (f. 4. c.) ; the mouth of the shell 
ovate, continued, rather angular behind, with 
a slightly thickened internal rib. 
and leaves of fresh-water plants. (See Pfeiffer ^ 
Moll t. 6. f. 10, 11, 12.) 
M. Moquin Tandon erroneously considers the Hy^ 
drobia of Hartmann, which has a subspiral horny 
operculum, as a sub-genus of Bithinia^ under the 
name of Bytliinella^ and gives the name Elona to 
the true Bithinice. 
Fig. 4. 
These animals are 
oviparous, their eggs 
being deposited in 
oblong groups, like 
the Limncei or Pond 
Snails, on the stems 
c 
Bithinia ventricosa. 
c, operculum. 
