328 
ZOOLOGY. 
margin, when extended, being almost straight, having a very faint tendency to lunation ; scales generally large. Colors of 
the fresh run fsh: hack of head, back, dorsal and caudal fins, bright blue, spotted on the head with roundish, on the fins with 
oval spots of black ; the blue of the back is silvery, that of the head and fins darker ; lower parts silvery white, this color 
extending about an inch above the lateral line, and merging itself irregularly into the color of the back ; no spots below the 
lateral line, which is faint and of a bluish dusky color ; lower fins pale and unspotted, their tips somewhat darkish. 
The specimen upon which the description of the present species is based was an adult female, 
obtained by the writer in the Straits of Fuca in February, 1857. Its body was fusiform, in its 
dorsal profile resembling somewhat the S. quinnat, Rich. It was, however, more slender than 
that species, and differed greatly in the form of the head and tail, besides having other marked 
characteristic distinctions. 
The following brief diagnosis may serve to assist in distinguishing the present species from 
its nearest relatives found in the same region: From S. quinnat , Rich., it may be known by the 
much smaller head and rounded, not pointed, snout. The smooth triangular projection extend¬ 
ing in front of the symphysis mentis of that species is also wanting. The tail of the adult 
S. quinnat is very deeply lunated, almost forked; that of the present species is so abruptly 
terminated that it has suggested the specific name applied, the end being almost as abruptly 
truncated as if chopped off with a large knife. In this respect it resembles the adult male of 
the Salmo trutta , Lin., as figured in Agassiz’s Histoire Naturelle des Poissons d'eau douce , 
Planches , Livraison I, Tab. VII. 
Another difference is in the greater size and thickness of the S. quinnat , which not unfre- 
quently attains a weight of thirty or forty pounds, whereas the present fish is usually found 
not exceeding ten or twelve pounds, and generally much less; and its common length, when 
full grown, rarely exceeds thirty-two inches. From the S. Gairdneri , of Richardson, (not of 
Girard, see pi. LXXI, Pacific Railroad Reports, which is drawn from the young of some other 
species,) it is more difficult to be distinguished, both having many characters in common. It is 
possible that hereafter, upon accurate comparison being made with numerous specimens, they 
may be found identical. In studying the specimens at present in the Smithsonian collection, 
we were obliged to confine ourselves to the examination of two imperfectly dried skins of the 
S. Gairdneri and one of the present species, which as yet are the only representatives of those 
species contained in the collection. The following differences, however, were found : the 
S. truncatus has the head smaller and shorter; tail neither so wide nor so long, and more 
spotted; teeth in the lower jaw more numerous, but smaller; muzzle and chin more pointed; 
body posterior to anal fin more slender. The lengths of the three skins were much the same, 
those of the S. Gairdneri being slightly greater. The teeth of the latter are larger and more 
scattered, being in one specimen 9 -9 and in the other 10-10 on the arms of the lower jaw. 
Those of the S. truncatus have 14-16 on each side, and, although in line, were dispersed in a 
pair-like manner— i. e., every other interval being greater. This pair-like disposition of the 
teeth is not seen in the S. Gairdneri. 
From the S. Gibbsii it may be known by its greater size and much brighter colors, propor¬ 
tionally smaller tail and fewer spots. The dental arrangement, however, is much the same, 
barring the absence in the S. Gibbsii of the pair-like distribution of the teeth already spoken of. 
This peculiar dental arrangement may be accidental in the specimen preserved, and has, 
therefore, not been included among the specific characters of the species. For the same reason 
the well-marked presence of a double row of teeth on the anterior portion of the vomer was not 
