SALMONOIDEiE. lbi 



of each scale is roundish, and its convex centre, having a greyish hue and silvery lustre, is 

 surrounded by a dark border of minute dots which are deficient or less numerous on the yel- 

 lowish-grey spots, and also on the bluish-white belly. The dorsal and caudal fins have the 

 greenish-grey tint of the back, and the ventrals and anal are muddy-orange, this colour also 

 partially tinging the pectorals. The irides are bright honey-yellow with blue clouds. The 

 teeth, gums, and roof of the mouth have a tinge of purple, whence Dr. Mitchill gave the 

 name of amethystus to the species. 



Scales moderately small, thin, flexible, obtusely oval, tiled, and firmly imbedded in the 

 skin ; the uncovered roundish part of each scale measures less than a line. The scales on 

 the under surface of the tail, and adjoining part of the belly, are rather larger, and those on 

 the lateral line, 133 in number, are mostly elliptical, being narrower and somewhat longer 

 than the others. About. 221 rows of scales meet at the lateral line, and a vertical row be- 

 neath the commencement of the dorsal contains 82, of which 32 are above the lateral line. 

 There are thirteen scales in a linear inch measured on the sides, and a single detached scale 

 measures about one line and three-quarters. The lateral line is about an inch nearer to the 

 dorsal than to the upper ventral ray. 



Form much like that of the Common salmon : the profile of the head and body bulges a 

 little, and the sides are somewhat flattened. The head forms one-fourth of the total length 

 from the snout to ihe tips of the caudal : it is flattish above and slightly convex in profile. 

 Radiating lines on the frontal bone appear through the dried skin, but the elevated central 

 ridge and curved lateral uneven ones, conspicuous in several of the trouts already described, 

 are nearly obsolete in this species. The skull is more bony than that of the Common salmon, 

 and the snout, instead of being cartilaginous, is formed of firm bone. Eye midway between 

 the tip of the snout and nape, and twice as near the former as to the hinder edge of the gill- 

 cover, the measurement being made from the centre of the pupil. There are seven diameters 

 and a half of the circular orbit in the total length of the head, and five and a half in that, of 

 its upper surface. The nostrils, consisting of two small contiguous orifices on each side, are 

 situated before and a little above the angle of the orbit : the foremost orifices have a soft ele- 

 vated edge, and are the largest. 



The jaws are very strong. In the male the upper one overlaps the conical knob of the 

 lower one by about half an inch : in the specimen now under consideration, which is supposed 

 to be a female, the jaws are nearly equal, but the soft parts have been partly eaten by insects. 

 The labials, not quite thrice the length of the inter maxillaries, are strong and nearly cylin- 

 drical (not a thin plate as in other trouts), and the appophysis, attached above like a crest, 

 projects beyond the limb of the bone, in which respect also this trout differs from its congeners. 

 The distance between the tip of the snout and lower extremity of the labial reaches from the 

 snout to about an inch beyond the orbit, falling fully three-quarters of an inch short of the 

 nape. The under jaw. thick and rounded, is articulated to the lower end of the preoperculum, 

 and also by a hinge-like joint to the jugal-bone. The length of the lower jaw is equal to that 

 of the upper surface of the head. The porous lines on the heads of other trouts exist like- 

 wise in this, being mostly connected with foramina in the bones. 



