214 Qiiarte? ly Journal of Conchology. 



and all the varieties of coloration are well represented by speci- 

 mens. To these remarks it should be added that T. Coosaensis 

 has so far pro'-en much more difficult to obtain than the other 

 species. Along with them are found the species of Schizostoma, 

 and those varying forms of Goniobasis, Anculosa and Lithasia which 

 have given rise to a multitude of doubtful species. 



A few words in regard to the Geographical distribution of the 

 North American Viviparidce seems to be in place here, in contrast 

 to the extremely limited range of the species in question. The 

 genus Melantho is found from Canada to the lower part of the Gulf 

 drainage, having its most ponderous forms and greatest diversity in 

 the central district of this range. The genus Lioplax extends from 

 New Jersey and Pennsylvania southward to the Gulf dramage, 

 having its most abnormal species in the Coosa river, associated 

 with Tulotma and ATelantho. Vivipara extends from Minnesota 

 to Mexico, and has its most highly developed forms in the same 

 region as Melantho, or, perhaps, more properly in its western half. 

 These shells are widely varied in different habitats, as to their size 

 and weight, but they never seem to lose their distinctive characters, 

 with the single exception of Melantho; and greater interest is added 

 to this fact, as we find specimens, identical in every respect, inhab 

 iting the extreme limits of distribution. I have recently obtained 

 V. intertexta from Lakes in Minnesota, identical with specimen 

 received from Louisiana at the same time. Likewise, the northern 

 specimens of Vivipara contectoides are identical, in every particular, 

 with those from Florida. 



In this same range the variation of the St7-epomatidm is so great 

 that there are no common species; the few northern forms of this 

 faniily entirely disappearing within the limits embraced by the Ohio 

 system of drainage. Though Limncea and Pliysa are sub-boreal 

 genera, a {&\n obscure species have a range far to the south, being 

 found in Texas and the other gulf states. But whether they are 



