REPORT ON ICHTHYOLOGY. 



By Prof. Theo. Gill. 



Smithsokian Institution, 



Washingto)!, December 1, 1860. 



Sir : I have the honor to forward to you the report on the ichthyology of your 

 expedition, which I have beeu requested to prepare. 



Ahhough few species of fishes were obtained, they are of nnich interest. Most 

 of them have been fully described in the accompanying report, even when not new, 

 as in the case of the species which is now called Plafi/(/ohio communis. As all the 

 groups to which the respective species belong are in some confusion and not Avell 

 restricted, I have been compelled to examine the history and nomenclature of not 

 only the o-enera to which thev are referable, but of tlie allied ones. As in almost all 

 the cases, such genera have been limited in a dift'erent manner and considerable modi- 

 fications introduced, I have always given the full generic characters, founded on a 

 personal examination, or a careful perusal of the descriptions of all the known species 

 of the genera. This I have considered to be the course most advantageous, under the 

 circumstances, to science. 



The classification which I have here followed is tliat ^vliich I have jn'oposed and 

 published in the Proceedings of the Academy of Natural Sciences of Philadelphia. 

 It may be considered a modification of that of the illustrious and learned Johannes 

 Miiller, whose recent death has been so much mourned Ijy naturali.^ts ; it diftcrs from 

 the Miillerian classification in the very different acceptation and resti'iction of the 

 orders and suborders. 



The investigations which have been undertaken in the preparation of the report 

 have been pursued in the Smithsonian Institution; and to the power of availing myself 

 of the excellent Library and Museum of the Institution, such value as the report may 



have is due. 



I am, sir, very truly yours, 



TuEO. Gill. 

 Capt. J. H. Simpson. 



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