SUCKLEY ^MONOGRAPH OF THE GENUS SALMO. 139 



29. SALMO LEWISI, Girard. 



LEWIS'S TROUT ; MISSOURI TROUT. 



SYH.—Sahno Jewisi, Grd., Pro. Acad. N. Sc, Phil., viii, 1856, p. 210 ;— Ibid., P. 

 R. E. Rep. Fishes, vol. x, p. 29 ; — Suckley, P. R. R. Rep., vol. xii, 

 p. 348, PI. Ixxi. [By mistake written ("*S« /mo .S'rtZa/' letvisiJ') The 

 '^salar" would have been stricken ont had the author read the 

 proof-sheets;] Ibid., Nat. Hist. Wash. Terr. 348, pi. 

 Salar lewisi. — Girard, in both the works already quoted. 



Sp. Ch. — Body somewhat thick ; back well arched ; head compara- 

 tively small, being contained a little more than five times in the total 

 length of the fish. Ground color of the upper region olivaceous; of the 

 lower, yellowish-white. The back, peduncle of tail, with the dorsal, adi- 

 pose, and caudal fins, are profusely sprinkled with stellate and irregular 

 black spots. The belly and lower fins are usually unspotted. Tail 

 somewhat notched. 



Young. — Resemble the young of S. virginalis. 



Diagnosis. — Salmo lewisi, Grd., is known from ;S^. virginalis, Grd., 

 by its smaller head ; the greater dorsal arch; its more deeply-notched 

 tail ; that of S. virginalis in the adult being nearly even; by having the 

 top of the head profusely spotted wit . black, and, by having a different 

 arrangement or plan of spot markings. The black spots are smaller, 

 more numerous, more irregular in shape in this species than in S. virgin- 

 alis, there being scarcely a well-rounded spot posterior to the middle of 

 dorsal fin. The spots on the tail are more numerous, but not so large. 

 The hues of this species are darker, audit is a stouter fish; its scales, 

 also, are larger. For comparative measurements of the head and body 

 see table 



The young of this species and the S. virginalis are very similar, and it 

 is only by a comparison of adults that strong diagnostic marks present 

 themselves. From Salmo iridea. Gibbons, this fish may be known by 

 having larger scales ; a much smaller head; dorsal outline more arched ; 

 head less sx)otted ; fewer spots on body anterior to a line drawn from 

 origin of dorsal to same of ventrals. These spots also are more sym- 

 metrically round. Those near the tail are very irregular and resemble 

 in shape those of the S. iridea. The tail of this fish, although mose cut 

 out than that of S. virginalis, is much less forked than that of 8. iridea. 

 Adults of the latter, of one footer more in length, show strongly-marked 

 forked tails. A good example of this is shown in specimen 59, sent from 

 Ohico Creek, California. From other species oif black-spotted trout the 

 diagnosis can be made up by reference to their descriptions. 



Hab. — Both slopes of the Rocky Mountains, north of the Souti Fass; 

 head-waters of the Missouri, (Dr. Suckley, Dr. Cooper.) Sou hciu 

 tributaries of the Yellowstone; Black Hills, Nebraska, (Dr. Hayden.) 

 Clarke's Fork of the Columbia, (Dr. Cooper, Mr. Gibbs, Dr. Kennerly.) 

 Kootenay River, (Dr. Kennerly.) Specimens have been received from all 



