Constantine Samuel Rafinesque. 97 



diversity that existed among the great family of the 

 Unionidce and attempted to render the group more 

 intelligible by instituting many subdivisions. That 

 these were always of value could not now be main 

 tained; but later students, unwilling to institute sub- 

 genera, have found it necessary to investigate these 

 mollusks under a natural grouping, each division of 

 which is headed by some well-known typical form. The 

 fact that Rafinesque actually made these divisions may 

 well be pardoned, therefore, in the light of the great 

 diversity of form which the Ohio Unionidtz present. 



Rafinesque visited the Falls of the Ohio for the first 

 time in the late summer of 1818. The water was low, 

 as it usually is at that season, and myriads upon myriads 

 of fresh-water univalves, of the family Strepomatidce, 

 were in the shallows and pools. The numbers of shells 

 of this group, which may be seen in a single pool, is 

 incredible to one who never has made a visit to the 

 locality. They are of various and beautiful coloration 

 or markings; to Rafinesque, who saw them for the first 

 time, they must have had an irresistible charm. Few 

 of the naturalists of America had seen more than the 

 half score of species found in the eastern States; these 

 western forms were practically unknown. They consti 

 tuted the subject of extended notice in the Brussels 



