34 



length three fourths of an ineJi. Loc. Fox river. The 

 shell has been referred by authors to various species 

 as only a reversed variety ; and I am inclined to so 

 consider it. 



MEI^A.^XIIO .«il lt*iiOI.II»l !<, Anthony. 



Shell ovate, thick ; whirls six ; suture distinct ; 

 aperture ovate ; spire elevated ; apex entire ; color 

 green ; length one and one-half inches. Abundant. 



This is one of our most abundant species, and is 

 considered by some to be a synonym of M. decisus. 

 It is a very variable shell in its characters. 



GENUS LIOPLAX, Thoschel. 



I.IOPI.AY SI KCAUi:^ATA, Say. 



Shell has six carinated whirls, wrinkled ; suture im- 

 pressed ; aperture oval ; color greenish ; length three- 

 fourths of an inch. Loc. Illinois i-iver. 



Say's description of this species was of a dwarfed 

 specimen and represents it as having but three whirls. 

 The foregoing are the prevailing species of Vivapara. 

 We have, however, 31. noarctata, Lea ; and M. rvfiis, 

 Halde, though specimens are not abundant. There 

 yet remains much work to be done before the true pos- 

 ition of some species is determined. 



FAMILY RISSOIDiE. 

 SUBFAMILY HY'DROBIN^. 



OK^il'iii AM.-^IC'OI.A, G. & II. 

 Amnicola. porata. Say. Shell obtUSe, COnic ; Volu- 



lions four, wrinkled ; spire obtuse ; labrum and labium 

 •equally rounded, umbilicus distinct ; shell rather short ; 



