286 Salmonidz 
The stomach in all the Salmonide@ is siphonal, and at the 
pylorus are many (15 to 200) comparatively large pyloric cceca, 
The air-bladder is large. The eggs are usually much larger 
than in fishes generally, and the ovaries are without special 
duct, the ova falling into the cavity of the abdomen before 
exclusion. The large size of the eggs, their lack of adhesive- 
ness, and the readiness with which they may be impregnated, 
render the Salmonide peculiarly adapted for artificial culture. 
The Salmonide are peculiar to the north temperate and 
Arctic regions, and within this range they are almost equally 
abundant wherever suitable waters occur. Some of the species, 
especially the larger ones, are marine and anadromous, living 
and growing in the sea, and ascending fresh waters to spawn. 
Still others live in running brooks, entering lakes or the sea 
when occasion serves, but not habitually doing so. Still others 
are lake fishes, approaching the shore or entering brooks in 
the spawning season, at other times retiring to waters of con- 
siderable depth. Some of them are active, voracious, and 
gamy, while others are comparatively defenseless and will not 
take the hook. They are divisible into ten easily recognized 
genera: Coregonus, Argyrosomus, Brachymystax, Stenodus, On- 
corhynchus, Salmo, Hucho, Cristivomer, Salvelinus, and Pleco- 
glossus, 
Fragments of fossil trout, very imperfectly known, are re- 
corded chiefly from Pleistocene deposits of Idaho, under the 
name of Rhabdofario lacustris. We have also received from 
Dr. John C. Merriam, from ferruginous sands of the same region, 
several fragments of jaws of salmon, in the hook-nosed condition, 
with enlarged teeth, showing that the present salmon-runs have 
been in operation for many thousands of years. Most other 
fragments hitherto referred to Salmonide belong to some other 
kind of fish. 
Coregonus, the Whitefish—The genus Coregonus, which in- 
cludes the various species known in America as lake whitefish, 
is distinguishable in general by the small size of its mouth, the 
weakness of its teeth, and the large size of its scales. The teeth, 
especially, are either reduced to slight asperities, or else are 
altogether wanting. The species reach a length of one to three 
feet. With scarcely an exception they inhabit clear lakes, 
