SUCCINEA. 71 



careous matter enough to give it consistency. In the 

 western States, and especially on the banks of the Mis- 

 sissippi it acquires more lime, and becomes somewhat 

 robust, and attains its greatest size. The largest speci- 

 mens we have seen, measuring one inch in extreme 

 length, were taken from the oozy mud left by the Mis- 

 sissippi in low places, by an inundation. Like the other 

 species, it prefers moist situations, but it is also spread 

 abroad upon the hill-sides, as in Vermont, at considerable 

 distances from water. 



When the shell is oval, the last whorl very ample and 

 expanded, forming nine-tenths of the whole volume, and 

 but httle oblique, the spii-e being at the same time very 

 small and not promment, and the aperture oval and well 

 rounded at both extremities it is the form described as 

 Succinea ovalis by Mr. Say. The variation to which it 

 is most subject is a lengthening and narrowing of all its 

 parts. The spire becomes more produced, and its con- 

 volutions less close ; the last whorl is compressed at the 

 sides, and more oblique. The aperture by this process 

 becomes elongated and narrow, and its posterior margm 

 more angulated. In this condition it is Succinea obliqua, 

 Say. The extremes of the two varieties differ much 

 from each other, yet they are blended together by almost 

 inappreciable degrees of variation, and we have never 

 met with specimens in the northern States which could 

 not be referred to one or the other of these varieties. 



Occurring as this species does, plentifully, over a 

 great part of the Union, and therefore everywhere 



