498 Bulletin 77, United States National Museum. 



■which mark the Cut-throat series of trout, or Salmo mykiss. These forms 

 are usually well separated from mykiss, on the oue haud, and from irideus 

 on the other. There is, however, a strange medley of forms apparently 

 aberrant or intermediate, confusing any attempt at specific definition. 



The following analytical key contrasts the two most clearly marked 

 varieties: 



a. Scales rather siiiall, averaging 155 cross series, the number varying from 130 to 180(ooiint- 



iug the obli(j\ie cross series above lateral lino). Sea-running forms reaching a large 



size ; weight of sea-ruu adult 8 tu -U pounds ; landlocked forms much smaller, down 



to 3^ pound. Coloration pale, with few spots. Columbia River and southward to San 



Francisco Bay. GAiRnNEiii, 780. 



aa. Scales larger, averaging about 135 cross series, the numlicr varying from 130 to 145. Lake 



forms ; coloration very silver^' and with few spots ; weight 3 to 10 pounds. Frasei 



River, etc. kamloops, 780a. 



Represented in large rivers and estuaries, especially from the Columbia 

 southward to Monterey, by the anadromous form, the typical 



780. SALMO GAIRDNERI, Richardson. 



(Steelhead; Hardiiead; Salmon Trout.) 



B. 12 or 11; D. 11; A. 12; scales usually about 150-28, varying in speci- 

 mens from Astoria from 137 to 177 (specimens counted by Cramer and 

 Otaki); pyloric cneca 42; vertebrje 38 + 20. Body rather stout, not very 

 deep mesially, but with the caudal peduncle thick. Head comparatively 

 short and rather slender, in the females small, in the males the jaws more 

 or less prolonged; maxillary rather narrow, the small eye nearly above its 

 middle; lower jaw included; upper jaw in males emarginate at tip and 

 at jun(ition of premaxillary. Teeth rather small, those on the vomer in 

 two long, alternating series, which are about as long as the palatine 

 series. Preopercle rather wide, with the lower limb short ; opercle mod- 

 erate. Gill rakers short and thick, 8 +.12 (essentially as in our other 

 species). Ventral appendage not half the length of the fin. Tail wide, 

 squarely truncate in the aduit, somewhat emarginate in the young. Flesh 

 rather pale. Bones much firmer than in On covin/ nchus. Color olive green 

 above; sides silvery ; head, back, upper fins, and tail moreor less densely 

 covered with black spots; belly usually unspotted; males with colors 

 heightened, the back greenish ; both sexes in spring with a broad flesh-col- 

 ored lateral band, deep rosy red on theopercles, this often retained through- 

 out the year; fins not red: no red on the membrane of lower jaw. Length 

 30 inches. Coastwise streams from Santa Ynez Mountains, Santa Barbara 

 County, California, northward to British Columbia, west of the Sierra 

 Nevada and Cascade Range, especially abundant in the Lower Columbia, 

 ascending the Snake River as far as Auger Falls. Also common in 

 Russian River and Klamath River. A large trout, abounding in 'the 

 mc'iths of the rivers, reaching a weight of 20 pounds or more, migra- 

 tory like the salmon, and ascending rivers fully as far. It spawns later 

 than the salmon, (in early spring in the Snake and Salmon rivers in 

 Idado), and is found in the lower part.s of the rivers, spent, at the time ol 

 the spring salmon run. It is then nearly useless as food, but at other 



