90 Salmonidae 



rhynchus. Two others more or less similar in character occur 

 in Japan and Kamchatka. The others (trout), forming the 

 subgenus Salar, are non-migratory, or at least irregularly 

 or imperfectly anadromous. The true or black-spotted trout 

 abound in all streams of northern Europe, northern Asia, and 

 in that part of North America which lies west of the Mississippi 

 Valley. The black-spotted trout are entirely wanting in eastern 

 America a remarkable fact in geographical distribution, perhaps 

 explained only on the hypothesis of the comparatively recent 

 and Eurasiatic origin of the group, which, we may suppose, has 

 not yet had opportunity to extend its range across the plains, 

 unsuitable for salmon life, which separate the upper Missouri 

 from the Great Lakes. 



The salmon (Salmo salar) is the only black-spotted sal- 

 monoid found in American waters tributary to the Atlantic. 

 In Europe, where other species similarly colored occur, the 

 species may be best distinguished by the fact that the teeth 

 on the shaft of the vomer mostly disappear with age. From 

 the only other species positively known, the salmon trout (Salmo 

 trutta), which shares this character, the true salmon may be 

 distinguished by the presence of but eleven scales between the 

 adipose fin and the lateral line, while Salmo trutta has about 

 fourteen. The scales are comparatively large in the salmon, 

 there being about one hundred and twenty-five in the lateral 

 line. The caudal fin, which is forked in the young, becomes, 

 as in other species of salmon, more or less truncate with age. 

 The pyloric cceca are fifty to sixty in number. 



The color in adults, according to Dr. Day, is "superiorly of 

 a steel-blue, becoming lighter on the sides and beneath. Mostly 

 a -few rounded or X-shaped spots scattered above the lateral 

 line and upper half of the head, being more numerous in the 

 female than in the male. Dorsal, caudal, and pectoral fins 

 dusky; ventrals and anal white, the former grayish internally. 

 Prior to entering fresh waters these fish are of a brilliant steel- 

 blue along the back, which becomes changed to a muddy tinge 

 when they enter rivers. After these fish have passed into the 

 fresh waters for the purpose of breeding, numerous orange 

 streaks appear in the cheeks of the male, and also spots or 

 even marks of the same, and likewise of a red color, on the body. 



