PHYSADiE. 



Gasteropodous monoicous inoperculate 

 pneumobranchiate testaceous aquatic mollusca; 

 having a single pair of triangular or filiform 

 contractile tentacles, the surface of which is 

 covered with vibrillss,* and having the eyes at 

 their internal base: the shells are thin in tex- 

 ture, of uniform tints, and with the margin of 

 the aperture sharp. 



The family Limneana of Lamarck, belongs 

 to Cuvier's Pulmonifera aquatica, of his order 

 Pulmonifera, and class Gasteropoda; to Blain- 

 ville's family Limnacea, of his order Pulmono- 

 branchiata, and sub-class Paracephalophora 



* Cilia of authors, which term, however, was preapplied, 

 and is still used, for hairs or bristles of a certain character. 

 Thus the mouth of an animalcule, and the legs of an 

 acarus, are both said to be ciliated. My friend Professor 

 Bailey, an acute microscopist, approves of the term I have 

 proposed for these vibratile organs. 



