APPENDIX TO THE UNIONID^ OF ALABAMA. 



The student who may desire to become acquainted with 

 the UnionidEe of Alabama, will naturally have his attention 

 drawn to some interesting facts relating to Geographical 

 Distribution. In some instances a species will be found to 

 occur in numerous localities, some of them beyond the lim- 

 its of the State. In other instances, species bearing a very 

 close resemblance to each other occupy stations apart from 

 each other, seldom occurring together. Many species are, 

 so far as is known, limited to a particular stream, or a portion 

 of a system of drainage. Among the species having widest 

 distribution, may be mentioned Unio Anodontoides, which 

 occurs in the Chattahoochee and Alabama rivers ; and is 

 also found in the Ohio river, and in some of the rivers in 

 Illinois. A group of species very strongly resembling each 

 other, embraces Unio acutissimus, U. parvulus, U. rubellinus, 

 and U. penidllatus* The two latter belong also to the State 

 of Georgia. Another group of species strongly resembling 

 each other, varying somewhat in size and other minor de- 

 tails, embraces Unio striatus, U. modicus, V. litus, and U. 

 striatulus, the last being found in North Carolina, and later 

 (according to Mr. Lea), in Georgia. 



Still another group embraces species, a portion of which 

 are found in adjoining States, as well as in Alabama. Cu- 

 riously, it appears that some of these species sometimes 

 unquestionably occur in the same station. This group em- 

 braces Unio decisus, U. concolor, U. consanguineus, U. clavus- 

 U. pallidofulvus, U. inter ventus, U, crebrivitiatus, and U. 

 Chattanoogaensis. In the Chattahoochee river, U. Sloatiaa, 

 nus takes the place of U. trapezoides, found in the Alabam, 



