PHYSA. 



125 



Genus PHYSA, Draparnaud. 



For description of the soft parts, see Halde- 

 man's Monograph, p. 20. Prof. Haldeman 

 was not aware that Ph. hypnorum differs from 

 the other species in the mantle margin being 

 without digitations, hence his remark that 

 " The animal is distinguished from Limnea by 

 the digitated mantle," etc., must be under- 

 stood to apply to the genus Physa as restricted 

 by subsequent authors. 



The argument of Prof H. (p. 22) in favor 

 of retaining Physa instead of the older name 

 BuUniis on the score of expediency would find 

 no favor at the present day, and the latter 

 name would have been adopted long since had 

 it not been discovered that the animal, instead 

 of being the same, is generically distinct. 



The following subgenera of Physa are ad- 

 mitted, — none of them containing many spe- 

 cies : 



(41) 



