33 



times seen in collections labeled drculus. Unio unicolor is 

 probably very similar to castaneus, 



Unio vallatus, of Bogue Chitto creek, and U. Cahabensis, 

 of the Cahawba river, very strongly resemble each other. 



Unio Edgarianus, of the Tennessee river and its tributa- 

 ries, is the type of a group of shells resembling each other 

 in several important particulars. U. obuncus, U. Tuscumbi- 

 ensis and U. Andersonensis belong to this group. 



Among the shells of the Alabama and Coosa rivers are 

 a few which remain to be noted as occurring in Tennessee, 

 Ohio, &c. ; U. metariever, U. cornutus, U. pyramidatus, U, 

 securis, and possibly U. plenus, may be incuded in this list. 

 Unio tuberculatus, which occurs in Alabama, is also found 

 in^Ohio and adjoining States. 



Unio subangulatus, of the Chattahoochee, is represented 

 in Buck creek by a larger shell of the same type, which 

 has not as yet been set apart as a distinct species. It may, 

 however, be regarded as being quite as distinct from sub- 

 angulatus as medius is from striatus in the Chattahoochee 

 system. 



In the Cahawba river three species are indicated, under 

 the names glandaceus, instructus and verus. Specimens evi- 

 dently referable to the three species have been submitted 

 for examination. They resemble each other very strongly 

 indeed, and differ simply as specimens of different ages and 

 sexes might be supposed to differ, when a single species is 

 subjected to a diversity of conditions. 



The student will find that quite a considerable number 

 of species originally quoted as found in various streams in 

 Georgia, have been catalogued as Alabama shells. Among 

 these is Unio radians, originally found in the Othcalooga 

 creek in Georgia. Shells from Alabama agreeing very ex- 

 actly with the description and figure of this species have 

 been submitted for examination. The shells that have 

 been examined are, without doubt, the female forms of an 

 Alabama species called U. plancus. The question of the 

 identity of radians and plancus is still an open one, in the 

 absence of Georgia specimens for comparison. 



