BITHINIA. -iO 



inner surface of the respiratory cavity; the 

 ridges narrow, slightly dilated, and angiilated 

 near the middle. {3Ioquin Tandon, t. 39. f. 31. 

 32.) Stomach with cartilaginous stylets. Male 

 organs at the hinder base of the right tentacle, 

 ahvays 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 claws, not withdrawn in the aperture of the 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. 



These animals are 

 oviparous, their eggs 

 being deposited in 

 oblong groups, like 



Bithinia ventricosa. the LimilCBi OX Pond 



C operculum. g^^^-jg^ ^^^ ^|^g ^^^^^ 



and leaves of fresh- water plants. (See Pfeiffer, 

 Moll t. 6. f. 10, 11, 12.) 



M. Moquin Tandon erroneously considers the Hy- 

 drohia of Hartmann, which has a subspiral horny 

 operculum, as a sub-genus of Bithinia, under the 

 name of Bythinella, and gives the name Elona to 

 the true Bithinice. 



