168 PROCEEDINGS OF THE ACADEMY OF [May-Oct., 



Planorbis marginatus (Miill.) Risso (97). This is Planorbis 

 suhmarginatus Cristofori and Jan. and, according to Bourguignat, 

 Helix compla7iaia Linne (var. B.). 



Planorbis carinatus (Miill.) Risso (97). Correct. 



Planorbis spirorbis (L.) Risso (97). Very poor specimens which 

 might be P. spirorbis Linne, or P. albus Miiller. 



Planorbis vortex (Miill.) Risso (98). Correct according to 

 Mortillet, but the shell has now disappeared from the collection. 



Planorbis nitidus (Miill.) Risso (98). The specimens in the 

 collection belong to two species, P. rotundatus Poiret, and P. vortex 

 Miiller. I have not found P. nitidus in the Alpes-Maritimes. 



Planorbis cristatus (Drap.) Risso (98). Correct. 



Planorbis reticulatus Risso (98). No longer in the collection. 

 Moquin Tandon confuses it with P. aMis Miiller, but it is not prob- 

 able that he was able to examine the type before its disappearance. 

 Risso queries its relation to that species. 



BITHYNIA Risso (100). This name was spelled Bithinia by 

 Gray in 1821 when he applied it to an undescribed new species (B. 

 ventrosa), but in 1824^ he states that Helix tentaculaia is the type 

 and names Prideaux as the author of the genus. It is very probable 

 that the English naturalist, Dr. Leach, communicated the name to 

 Risso when he came to pass the season at Nice in 1820. Many 

 authors write Bythinia, deriving the name from the Greek word 

 signifjdng ''those who live at the bottom of the water." 



BiTHYNiA JACULATOR (Miill.) Risso (100). This is the Helix 

 tentaculata Gmelin, very common in the Department. 



BiTHYNiA MERiDiONALis Risso (100, fig. 28). Avmicola similis 

 (Drap.). 



Valvata PLANORBIS (Drap.) Risso (101). Bourguignat notes three 

 species in this carton, V. piscinalis Ferussac pere, V. spirorbis Drapar- 

 naud, and a species near V. cristata Miiller. The latter has never 

 been announced from the Alpes-Maritimes. 



Valvata minuta (Drap.) Risso (101). Extremely young speci- 

 mens of Bithinia tentaculata Linne. 



s Phil. Mag. & Journ., Ixiii, 1824, p. 277. 



