PALUDINA SUBCARINATA. 9 



cent, with from four to six ventricose volutions, 

 which are covered with numerous fine trans- 

 verse elevated striae: apex pointed: suture deeply 

 impressed and canaliculate: aperture regularly 

 ovate, rounded posteriorly: peristome entire. 

 The later additions of the opercle are concen- 

 tric, whilst the centre is subspiral. 



Color of the outside very light brownish- 

 green; inside bluish-white. 



Geographical Distribution. Found in the 

 Delaware, Schuylkill, and Susquehanna rivers: 

 near Cincinnati, Ohio, J. G. Anthony. 



OBSERVATIONS. 



This species is closely allied to the preced- 

 ing, both in external form and general habits, 

 so that the natural history of one is that of the 

 other. The shell may be distinguished from 

 that of P. decisa by the subrotund aperture, 

 pointed apex, elevated striae, and dull exterior. 

 Those inhabiting running waters have the shell 

 thick and opaque, with the apex eroded. The 

 orange spots upon the animal are lighter and 

 smaller than in the preceding species. 



The young, when first excluded throughout 

 the spring and summer, are spirally striated, 



F 2 



