98 Salmonide 
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 masont, 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- 
