THE ROCKY MOUNTAIN TROUT. 2?I 



CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY. 



Salmo purpuratus Pallas. Salmon Trout of the Columbia ; 

 Yellowstone Trout ; Rocky Mountain Brook Trout; Lake 



Trout. 



Bod)' moderate elongate, compressed. Head rather short, 

 mouth moderate, the maxillary not reaching far beyond the 

 eyes. Vomerine teeth as usual, set in an irregular zigzag se- 

 ries; teeth on the hyoid bone normally present, but often obso- 

 lete, especially in old examples. Dorsal fin rather low; cau- 

 dal fin slightly forked, less so than in iridcns [This is the 

 California Brook Trout ox Rainbow Trout], more than in spi 'tu- 

 rns [Rio Grande Trout], the caudal more forked in )'oung indi- 

 viduals than in the adult, as in all Trout. Scales moderate, 

 varying to rather small. Back and caudal peduncle profusely 

 covered with rounded black spots of varying size; dorsal, cau- 

 dal and adipose fin covered with small black spots about as 

 large as the nostril; a few spots on the head; belly rarely spot- 

 ted ; inner edge of the mandibles below with a red blotch; 

 sea-run specimens are nearly uniform silvery; males with 

 a broad lateral band and patches of light red; extremely 

 variable in color and form. Head 4; depth 4. D. 10 A. 

 10.; Caeca 43. Scales variable in size, 33 150 30 to 39 

 170 30. The common Trout of the Rocky Mountains 

 and Cascade region, abounding in all the streams of 

 Alaska, Oregon and Washington, where it descends to salt 

 water, and reaches a weight of twenty pounds (Columbia 

 River, Charles J. Smith); also in the Yellowstone Region, 

 the Upper Missouri, the Upper Rio Grande, Colorado, and 

 the lakes of the Great Basin of Utah, being very abundant in 

 Utah Lake. Not common south of Mount Shasta in Califor- 

 nia. This species is apparently the parent stock, from which 

 our other Black-spotted Trout have scarcely yet become dif- 

 ferentiated. Considerable local variations occur, especially in 

 size, coloration, and size of scales. The red blotches on the 

 lower jaw between the dentary bones and the membrane join- 

 ing them is very constant and characteristic. [Synonomy.] 



{Sal/no purpuratus, Pallas, Zool. Ross. Asiat. iii, 374, 18 ri 

 31: Salmo clarki, Rich. Fauna Bor. Amer. iii, 224, 1836: 

 Fario stellatus, Girard, Proc. Acad., Nat. Sci. Phila. 219, 1856; 

 Salmo brevicauda Suckley, Am. Lye. Nat. Hist. N. Y. vii, 308, 

 1 861: Salmo steliratus, gibbsi, 3 and brevicauda, Gunther, vi. 117 

 120; Salmo clarki, Jordan, Proc. U. S. Nat. Mus. i, 77; Salmo 

 tsuppitch, Jordan, Proc. U. S. Nat. Mus. i, 72; Fario aurora,Girard, 



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