408 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



pies has been made, it has been necessary to iuclude all the species 

 described, in spite of the probability that not half of them are valid — 

 as we have no means of determining icMch half. I hope, however, soon 

 to be able to examine the original typical specimens, or, still better, to 

 make further collections in the same localities. 



In case of species which are for various reasons considered doubtful, 

 the nature of the doubt has been indicated as follows: d. s., a doubtful 

 species; d. a. s., doubtful as to species, i.e., doubt as to correctness of 

 identification ; d. g., doubtful as to genus. Species so loosely described 

 as to be of uncertain genus are, however, generally omitted. 



Varieties or subspecies have been generally omitted. There can be 

 no doubt that a full study of our fishes will necessitate the recognition 

 by name of varieties or subspecies, whatever called, in th6 case of nearly 

 every widely diffused form. In very few cases, however, have these 

 received names, except incidentally when described as new species, 

 and in still fewer have they been proi)erly limited and defined. Their 

 study and definition are therefore a matter for future work. 



The number of nominal Species Included in this catalogue is 665, 

 which are distributed in 157 genera. In Jordan and Copeland's Check 

 List, the number of species is about 670, arranged in 150 genera. The 

 total number of admitted species therefore has been slightly dimin- 

 ished (the ground covered in this list being greater), although upward 

 of forty new species have been added since the publication of the 

 first list. The reduction has been chiefly in the Salmonidw, Siluridce, 

 and Catoslomidcc. A considerable number of species doubtless remains 

 to be disc6vered in the Southern and Southwestern parts of the United 

 States, particularly in the ponds and bayous of the lowlands, while the 

 number of species of Cyprinidce and Cyprinodontidce must be further re- 

 duced. The total number of species will therefore not vary far from 680. 

 The number of genera admitted has been steadily increasing, and will 

 lirobably in time reach about200, unless succeeding ichthyologists adopt a 

 different standard of generic values from that which at present obtains. 

 Subgenera have been recognized for the more strongly marked sections, 

 and several new ones have been here indicated, most of which, however, 

 need no distinctive name. 



