FISHES—SALMONIDAE—FA RIO AURORA 
309 
advance of the dorsal fin, enters four times and a half in the total length. Its profile is 
fusiform. The head is rather small and conical, forming the fourth of the entire length, 
excluding the caudal fin ; the snout is rounded, sub-conical, protruding beyond the lower jaw. 
It is probable that in larger specimens it protrudes a great deal more, and especially more so in 
the male than in the female. The mouth is deeply cleft; the maxillary is rather narrow, and 
its free extremity extends to a vertical line passing considerably behind the orbit. The teeth are 
but moderately developed and very acute. An irregular row may be observed upon the shaft of 
the vomer, and a few smaller ones on the front of the same hone. The lingual series are 
parallel. The eye is of moderate development, sub-circular in shape ; its horizontal diameter 
being contained about four times and a half in the length of the side of the head. The opercle 
is much higher than broad, and narrower above than below ; its situation being very oblique. 
The sub-opercle is gracefully rounded exteriorly and hut moderately developed. The branchi- 
ostegals are eleven on either side. The anterior margin of the dorsal is equidistant between 
the snout and the insertion of the caudal fin ; its height is equal to its base, hut its posterior 
margin is not quite the half of the anterior ; it is composed of twelve rays, the anterior two of 
which being rudimentary. The adipose fin is very slender, and situated opposite the posterior 
portion of the anal. The latter is deeper than long, hut resembles the dorsal in its general 
outline ; it contains thirteen rays, the anterior two of which being likewise rudimentary. The 
posterior margin of the caudal is furcated ; the length of that fin enters about seven times and a 
half in the entire length of the fish. The origin of the ventrals is situated opposite the fourth 
developed ray of the dorsal or sixth in the series; these fins are composed of nine rays, the tips 
of which do not quite extend as far posteriorly as the tips of the posterior rays of the dorsal. 
The pectorals are rather small, broad upon their exterior and expanded margin, and composed 
of fourteen rays. 
Br. 11: 11; D 12 ; 0 ; A 13 ; C 8, 1, 9, 8, 1, 7 ; V 9 ; P 14. 
The rays in all the fins are bifurcated or branched, with the exception of the external caudal 
rays, and the rudimentary ones, as a matter of course. 
The scales are of hut moderate development; they are sub-elliptically elongated, somewhat 
irregular in their outline, and imbricated for nearly the half of their longitudinal diameter. 
Those constituting the lateral line are more elongated than the rest, with the concentric stria 
obliterated upon their posterior margin (fig. 30.) 
The coloration as observed on specimens preserved in alcohol is very much altered indeed. A 
uniform greyish tint seem to pervade all over the dorsal region. The sides are silvery, whilst 
the abdomen appears to have been of a deep orange, which is traceable over the lower fins. 
The upper surface of the head is uniform greyish black, whilst the cheeks and opercular 
apparatus are of a pure silver hue. The dorsal fin alone exhibits black spots ; the latter may 
have existed on the caudal fin. 
Specimens of this species were collected at Astoria, Oregon Territory, by Lieut. W. P. 
Trowbridge. 
References to the figures. —Plate LXVIII, fig. 1, represents Fario aurora , somewhat reduced 
in size. 
Fig. 2 is a scale from the dorsal region taken midway between the lateral line and the 
dorsal fin. 
Fig. 3, a scale of the lateral line. 
