EDITORIAL INTRODUCTION. xli 
The differences respecting specific nomenclature now are the results 
of differences of opinion as to seven points: (1) as to limits of genera; 
(2) as to limits of species; (3) as to the starting-point for nomenclature 
(4.e, whether 1758 or 1766); (4) as to the limits of priority and adhesion to 
rules of nomenclature; (5) as to latitude allowable in interpretation of 
descriptions ; (6) as to admission of extraneous evidence in interpretation 
of a printed description ; and (7) as to admissibility of names which deviate 
from classical correctness... 
In the lists of species now given, the rules prevalent among American 
naturalists and especially incorporated in the Canons formulated by the 
Union of American Ornithologists are adopted. The differences between 
the names now used and those employed by Dr. Goode are due to one or 
other of the causes just enumerated. They are the results of the great 
activity in new collecting and overhauling the records of the past since 
Dr. Goode’s work was first printed. 
IV. SYSTEMATIC INDEX OF SPECIES. 
(A) FRESH-WATER FISHES OF THE MISSISSIPPI VALLEY AND 
ATLANTIC SLOPE. 
The headquarters for the fishes of the cismontane region is in the lower 
and middle Mississippi valley. Therein the chief families are represented, 
and most of them in their greatest richness. Therein occur numerous 
species of small Cyprinids, Etheostomine Percids, and Centrarchids, as well 
as representatives of the peculiar American families of Lepisosteids, Amiids, 
Hyodontids, Percopsids, Amblyopsids, Aphredoderids, and Elassomids. In- 
deed, with the exception of the Characinids, Argentinids, Thymallids, Dalliids, 
Embiotocids, Cichlids, and Gadids, all of the thirty-four families of fishes, 
represented by permanent fresh-water members, are present in the Missis- 
sippi valley. The families excepted are of slight extent, numbering only 
one or two species, or, as in the case of the Characinids and Cichlids, 
represented only by outliers, the great hosts being otherwise inhabitants of 
the tropics. More fresh-water species may be found in some counties of 
limited extent in this region than in many States to the eastward or west- 
ward. ‘The angle-fishes, or those of direct economical importance, however, 
are not in proportion to the number of species. 
As the traveller progresses to the north, the species become fewer and 
fewer, and those characteristic of the north and congeneric with species of 
