SALMONOIDE.E. 165 



ridge, passing through the middle of the sub-orbitar bones. These pores exist in other trouts, 

 but are rendered conspicuous in this species by the prominence of the ridges with which they 

 are connected. Eye equidistant from the tip of the snout and nape. The orbit has an oval 

 shape, and the nostrils are rather nearer to it than to the tip of the snout. Labials thin and 

 of a narrow lanceolate form. The distance from the snout to the tip of the labial reaches 

 from the former to the nape, and extends beyond the posterior sub-orbitar bones. The lower 

 iaw is long, exceeding the length of the upper surface of the head by an inch and a quarter -. 

 its tip is a small incurvated knob. In the general form of the head the S. Rossii strongly 

 resembles the British species figured in Plate 91, f. 2 : it differs in the greater length of the 

 jaws, in the whole margin of the intermaxillaries being toothed, and in other particulars 

 readily discoverable by comparing the plates, — the British fish has an edentate depression at 

 the extremity of the snout for the reception of the knob of the lower jaw. 



Teeth. — In the only specimen I have had an opportunity of examining, part of the teeth 

 have been injured and removed. They appear to have stood in a single series on the upper 

 and lower jaws : the remaining ones are short, straight, and mostly obtuse, as if worn ; there 

 is also a single row of short, conical, but very acute teeth on each palate-bone ; and though the 

 vomer has been broken in preparing the specimen, two similar teeth remain on its anterior 

 extremity, and one farther back. The teeth on the tongue, amounting to about thirty, are 

 smaller and more crowded than the palatine ones ; they form two or more rows across the tip 

 and one down each side. 



Gill-covers. — Operculum rhomboidal with the corners rounded, its height being nearly 

 twice its breadth. The suboperculum has the same form in a different position, its length 

 corresponding with the breadth of the operculum. Both these bones are marked with cir- 

 cular indented lines crossed by straight ones radiating from the centre. The posterior edge 

 of the interoperculum is indented and somewhat concave. Preoperculum rather wide, its 

 breadth being about half that of the operculum : on its middle there are raised diverging 

 tubular ridges, and fine lines radiating from its centre to its posterior margin. The posterior 

 edge of the gill-cover is inclined to the under one at an acute angle, the corner formed by the 

 suboperculum being rounded. The gill-rays are flat, twelve on the right side and thirteen 

 on the left. 



Fins.— Br. 12—13; D 13—0; P. 14; V. 10, A. 11 ; C. 2l£, 



The dorsal has thirteen rays, the first scarcely perceptible, the next also short, the third 

 one quarter shorter than the fourth, which is the longest : the ninth ray is exactly opposite 

 to the origin of the ventrals, and stands midway between the tips of the snout and of the cen- 

 tral caudal rays : the last ray is divided to the base. The adipose fin is opposite to the 

 penultimate anal ray. The pectorals are scimitar-shaped and contain fourteen rays. The 

 ventrals have ten rays and the usual scaly appendages. The anal has eleven rays, of which 

 the fourth and fifth are the longest. The caudal fin is forked, and contains twenty-one broad 

 deeply -divided rays, with six short basal ones above and below. 



Scales. — This species differs remarkably from all the American trouts that have come 

 under my observation (except, perhaps, S. Hearnii) in the scales. They are small, particu- 



