CHAPTER V 
SALMONIDA— (Continued) 
ALMO, the Trout and Atlantic Salmon.—The genus 
Salmo comprises those forms of salmon which have 
been longest known. As in related genera, the mouth 
is large, and the jaws, palatines, and tongue are armed with 
strong teeth. The vomer is flat, its shaft not depressed below 
the level of the head or chevron (the anterior end). There are 
a few teeth on the chevron; and behind it, on the shaft, there 
is either a double series of teeth or an irregular single series. 
These teeth in the true salmon disappear with age, but in 
the others (the black-spotted trout) they are persistent. The 
scales are silvery and moderate or small in size. There are g 
to 11 developed rays in the anal fin. The caudal fin is truncate, 
or variously concave or forked. There are usually 4o to 70 
pyloric coeca, 11 or 12 branchiostegals, and about 20 (8+12) 
gill-rakers. The sexual peculiarities are in general less marked 
than in Oncorhynchus; they are also greater in the anadromous 
species than in those which inhabit fresh waters. In general 
the male in the breeding season is redder, its jaws are prolonged, 
the front teeth enlarged, the lower jaw turned upwards at the 
end, and the upper jaw notched, or sometimes even perforated, 
by the tip of the lower. All the species of Salmo (like those of 
Oncorhynchus) are more or less spotted with black. Unlike 
the species of Oncorhynchus, the species of Salmo feed more or less 
while in fresh water, and the individuals for the most part 
do not die after spawning, although many old males do thus 
perish. 
The Atlantic Salmon._-The large species of Salmo, called 
salmon by English-speaking people (Salmo salar, Salmo trutia), 
are marine and anadromous, taking the place in the North 
Atlantic occupied in the North Pacific by the species of Onco- 
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