876 FISHES—SALMONIDA. 
Description.—Body closely compressed, becoming deep in the adult; eye moderate, 
smaller than in other species, about 34 in head, the maxillary reaching to beyond its 
middle; back less arched, snout blunter and more elevated than in 7. tergisus, mouth 
larger and more oblique; pectorals longer and ventrals shorter than in Z. tergisus; belly 
carinated both before and behind ventrals; bluish, sides silvery, with golden luster ; 
head 4 3-4; depth 34; D. 9; A. 32; scales 6.56.7. 
Habitat, Ohio River to the Saskatchawan ; common northward. 
Diagnosis.—From Hyodon tergisus, this species may be known by its 
short dorsal, of but nine developed rays, and by the carination of the 
whole ventral edge. 
Habits.—Nothing distinctive is known of the habits of this species. 
Originally described by Rafinesque from the Falls of the Ohio, its occur- 
rence southward has been overlooked until very lately. In 1826 it was 
found in the Saskatchawan River by Sir John Richardson, and later by 
Dr. Coues in the Upper Missouri. In 1880 the writer obtained numer- 
ous specimens at the Falls of the Ohio, and was thus enabled to recog- 
nize the Amphiodon alosoides of Rafinesque. The species will doubtless 
be found in all the larger rivers of the Northwest. A third species, 
Hyodon selenops, Jordan and Bean, occurs in the rivers of the Southern 
States, but has not yet been seen in Ohio. 
FAMILY XIII. SALMONIDA. THE SALMONS. 
Body oblong or elongate, covered with cycloid scales; head naked; mouth terminal, 
varying much in size and form; maxillary forming the lateral margin of the upper jaw, 
provided with a supplemental bone, premaxillaries not pr otractile ; teeth various, some- 
times}wanting ; gills four, a)slit behind the fourth; pseudobranchie present, but often 
small or rudimentary ; gill-rakers moderate; gill-membranes not connected, free from 
the isthmus; branchiostegals 6-20; no barbels; dorsal usually median, not greatly 
elongate; adipose fin present; caudal fin forked; anal fin moderate or rather long; 
ventrals moderate, nearly median ; pectorals placed low; lateral line present; abdomen | 
rounded ; air-bladder large; stomach cecal or siphonal, the pyloric ceca few or many, 
sometimes obsolete ; ova generally large, falling into the cavity of the abdomen before 
exclusion; genera about 20; species 125, a large and varied family. Its members in- 
habit chiefly the fresh waters of northern regions, many of them being anadromous, run- 
ning up from the sea to spawn in the rivers. One genus, Retropinna, is found in New 
Zealand, and the species of Microstoma, Argentina, and Silus are mostly deep-sea fishes. 
In economic importance this family ranks among the very first, and the Salmon and 
Trout in all northern regions are the choicest prize of the angler. 
ANALYSIS OF GENERA OF SALMONIDZ, 
a, Pyloric ceca many; stomach siphonal. 
b. Jaws toothless or nearly so; scales large. (Coregonine.) 
c. Maxillary short and bona! : 5 F : .  CoreEGoxUs. 49. 
bb. Jaws with distinct teeth ; scales mostly cate ( Salmonine.) 
