162 LOWER VERTEBRATES. 



species of charr, altiiough from an sesthetic point of view it must be regarded as 

 inferior to all of thfi Salvelini. The largest river trout recorded by Dr. Day weighed 

 twenty-one pounds. Such large individuals are usually found in lakes in the north, 

 well stocked with smaller fishes 071 which the trout may feed. Farther south, where 

 the surroundings are less favorable to trout-life, they become mature at a length of 

 less than a foot, and a weight of a few ounces. These excessive variations in the size 

 of individuals have received too little notice from students of Salmonidse. Similar 

 variations occur in all the non-migratory species of Salmo and of Salvelinus. Numer- 

 ous river-trout have been recorded from northern Asia, but as yet nothing can be 

 definitely stated as to the number of species actually existing. 



In North America, only the region west of the Mississippi Valley and the valley of 

 Mackenzie River, have species of black-spotted trout. If we are to follow the usage 

 of the names salmon and trout, which prevails in England, we should say that it is 

 only these western regions which have any trout at all. Of the number of species 

 (about twenty in all), which have been indicated by authors, certainly not more than 

 four can really be regarded as distinct species, and of these four, two are, as will be 

 seen, still somewhat doubtful. The other names are either useless synonyms, or else 

 they have been applied to local varieties which pass by degrees into the ordinary types. 



Of the American species, the rainbow trout {Sahno irideus) most nearly approaches 

 the European Salmo fario. It has the scales comparatively large, although rather 

 smaller than in Salmo fario, the usual number in a longitudinal series being about 135. 

 The mouth is smaller than in the 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 color, as in all the other sjjecies, is bluish, 

 the sides silvery ia 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. In specimens taken in the sea, this species, like most other trout 

 in similar conditions, 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 northward to Mount Shasta, and occasionally 

 in coastwise streams to Alaska. No specimens have been anywhere obtained to the 

 eastward of the Cascade range or of the Sierra Nevada. 



It varies much in size, specimens from northern California often reaching a weight 

 of six pounds, while in the Rio San Luis Rey, the southernmost locality from which I 

 have obtained trout, they seldom exceed a length of six inches. Although not 

 an anadromous species, the rainbow trout frequently moves about in the rivers, and it 

 often enters the sea. Several attempts have been made to introduce it in eastern 

 streams. It is apparently more hardy and less greedy than the American charr, or 

 brook trout ( Salvelinus foiitinalis) . On the other hand, it is distinctly inferior to the 

 latter in beauty and in gaminess. 



The steel-head (Salmo gairdneri) is a large trout, of fifteen to twenty pounds in 

 weight, found very abundantly in the mouth of the Columbia and other rivers, in the 

 spring, at the time of the early salmon run. These are evidently spent fishes, indicat- 

 ing a spawning time later (probably mid-winter) than that of the salmon, and their 

 occurrence in the rivers at the salmon run is evidently due to a return toward the sea. 

 Steel-heads are occasionally taken in the Sacramento, but in the Columbia they are 

 abundant. They are rejected by the salmon fishermen, as their flesh is pale, and the 

 bones are much more firmly ossified than in the species of Oncorhynchits. The 



