PREFACE. 



In this memoir we have endeavored to give concise descriptions of 

 all the species of fishes known to inhabit the waters of Forth America, 

 north of the boundary between the United States and Mexico. 



The classification which we have adopted is essentially based on the 

 views of Professors Gill and Cope, who have, it seems to us, been more 

 fortunate in reflecting nature in their groupings of the fishes than have 

 any of the European systematists. In our arrangement of the families 

 and genera, we have endeavored to avoid, on the one hand, unnatural 

 associations, and on the other, subdivision beyond reasonable limits. 

 Genera to which we have been unable to give precise definition have 

 been rarely adopted. 



The rules of nomenclature generally recognized by naturalists, and 

 recently admirably formulated by Mr. W. H. Dall, have been followed 

 without deviation, except such as may be due to ignorance of all the 

 facts in any particular case. Most of the present confusion in nomen- 

 clature is due to the neglect of established rules, and the only way out 

 of this confusion is through the rigid enforcement of these rules. There 

 is little hope for uniformity in nomenclature so long as individual prefer- 

 ence or caprice is allowed to affect it. 



We are under obligations to Prof. Spencer F. Baird, to Prof. G. 

 Brown Goode, and to Dr. Tarletou H. Bean, for many aids, especially 

 in connection with our use of the specimens in the United States Na 

 tional Museum. To Dr. Bean, in particular, we have been indebted for 

 help of various sorts, including many unpublished notes. To Dr. Theo- 

 dore Gill and to Prof. E. D. Cope, we are indebted for numerous aids 

 and suggestions. Mr. Samuel Garman, of the Museum of Comparative 

 Zoology, has given us considerable assistance on the Elasmobrauchs. 

 Mr. Chas. L. McKay, of the United States Signal Service, has revised 



