The Rio Grande trout (_Salmo clarkii spilurus_) is a large and profusely spotted trout, found in the head-waters of the Rio Grande, the mountain streams of the Great Basin of Utah, and as far south as the northern part of Chihuahua. Its scales are still smaller than those of the ordinary cutthroat-trout, and the black spots are chiefly confined to the tail. Closely related to it is the trout of the Colorado Basin, _Salmo clarkii pleuriticus_, a large and handsome trout with very small scales, much sought by anglers in western Colorado, and abounding in all suitable streams throughout the Colorado Basin. =Hucho, the Huchen.=—The genus _Hucho_ has been framed for the Huchen or Rothfisch (_Hucho hucho_) of the Danube, a very large trout, differing from the genus _Salmo_ in having no teeth on the shaft of the vomer, and from the _Salvelini_ at least in form and coloration. The huchen is a long and slender, somewhat pike-like fish, with depressed snout and strong teeth. The color is silvery, sprinkled with small black dots. It reaches a size little inferior to that of the salmon, and it is said to be an excellent food-fish. In northern Japan is a similar species, _Hucho blackistoni_, locally known as Ito, a large and handsome trout with very slender body, reaching a length of 2½ feet. It is well worthy of introduction into American and European waters. [Illustration: FIG. 71.—Ito, _Hucho blackistoni_ (Hilgendorf). Hokkaido, Japan. ] =Salvelinus, the Charr.=—The genus _Salvelinus_ comprises the finest of the _Salmonidæ_, from the point of view of the angler or the artist. In England the species are known as charr or char, in contradistinction to the black-spotted species of _Salmo_, which are called trout. The former name has unfortunately been lost in America, where the name "trout" is given indiscriminately to both groups, and, still worse, to numerous other fishes (_Micropterus_, _Hexagrammos_, _Cynoscion_, _Agonostomus_) wholly unlike the _Salmonidæ_ in all respects. It is sometimes said that "the American brook-trout is no trout, nothing but a charr," almost as though "charr" were a word of reproach. Nothing higher, however, can be said of a salmonoid than that it is a "charr." The technical character of the genus _Salvelinus_ lies in the form of its vomer. This is deeper than in _Salmo_; and when the flesh is removed the bone is found to be somewhat boat-shaped above, and with the shaft depressed and out of the line of the head of the vomer. Only the head or chevron is armed with teeth, and the shaft is covered by skin.