98 Salmonidas 



series being about 135. The mouth is smaller than in other 

 American trout; the maxillary, except in old males, rarely 

 extending beyond the eye. The caudal fin is well forked, 

 becoming in very old fishes more nearly truncate. The head 

 is relatively large, about four times in the total length. The 

 size of the head forms the best distinctive character. The 

 color, as in all the other species, is bluish, the sides silvery in 

 the males, with a red lateral band, and reddish and dusky 

 blotches. The head, back, and upper fins are sprinkled with 

 round black spots, which are very variable in number, those 

 on the dorsal usually in about nine rows. In specimens taken 



FIG. 61. Rainbow Trout (male), Salmo irideus shasta Jordan. (Photograph by 



Cloudsley Rutter.) 



in the sea this species, like most other trout in similar con- 

 ditions, is bright silvery, and sometimes immaculate. This 

 species is especially characteristic of the waters of California. 

 It abounds in every clear brook, from the Mexican line north- 

 ward to Mount Shasta, or beyond, the species passing in the 

 Columbia region by degrees into the species or form known as 

 Salmo masoni, the Oregon rainbow trout, a small rainbow trout 

 common in the forest streams of Oregon, with smaller mouth and 

 fewer spots on the dorsal. No true rainbow trout have been 

 anywhere obtained to the eastward of the Cascade Range or 

 of the Sierra Nevada, except as artificially planted in the Tru- 

 ckee River. The species varies much in size ; specimens from 

 northern California often reach a weight of six pounds, while 

 in the streams above Tia Juana in Lower California the south- 



