OF CONCHOLOGY. 131 



STREPHOBASIS. 



Several of the species are reported only from East 

 Tennessee, while two of them occur in the branches of the 

 Alabama Eiver. One of these is found in both rivers. Prof. 

 Haldeman is in error in assis-ninsr Ohio Eiver as the habitat 

 of his St. curta. It has never been found there, but is one of 

 the most plentiful shells of the Tennessee Eiver, and as such, 

 is in all our cabinets. 



Goniohasic Section. 



These shells constitute three-fifths of the species of Strepo- 

 onatidse. They are naturally divided into two type forms : 

 the first, heavy, compact, with large subcylindrical body and 

 short spire, is eminently characteristic of the Coosa Eiver ; 

 while the second, containing narrow, elongated species, with 

 high spires of many whorls, although more extensively dis- 

 tributed, is still very characteristic of the waters of the 

 Tennessee Eiver and branches. 



To the first of these forms undoubtedly belongs Eurycse- 

 lon, a new genus, which probably includes more species than 

 have yet been assigned to it;— and /cS'j/w"so5to?/ia. Of the six species 

 of the former, one is from the Holston, another from the Cum- 

 berland, and the balance from the tributaries of the Alabama 

 Eiver. 



SCHIZOSTOMA. 



This genus, embracing twenty-six species, divided into two 

 distinct groups of nearly equal respective numbers, inhabits 

 the Coosa Eiver only, and in this limited space exhibits all 

 the range of variation in form, size and ornamentation, 

 belonging to genera which possess a more extended geo- 

 graphical distribution. 



MESESCHIZA 



Contains at present only the type species. It is a very 

 small, fragile shell, inhabiting the Wabash Eiver, and does 

 not appear to be of mature growth. 



GONIOBASIS. 



This ver}'- large and widely-extended genus embraces over 

 two hundred and fifty species, — more than half of all the 

 Strepomatidse, — and includes the only representatives of the 

 family west of the Eocky Mountains, or south of the United 

 States. 



One species, beautifully ridged with sharp, revolving ribs, — 

 the G. proscissa, of Anthony, — is reported simply from 

 northern Alabama. There are eighteen tuberculate species ; 

 the heavy, compact ones being principally from the branches 



