174 UNIVERSITY OF COLORADO STUDIES 
3. Black spotted species; vomer flat . . . uA ae se heer 68 ok yt 
Spotted with red or gray; vomer boat- habed | Reyes tee Xi tte LO, 
4. Scales typically large, in 120 to 130 cross series; but: varying ae 115 to 180; usually 
no red on throat; mouth small; size moderate (Montana, introduced) 
S. irideus Gibbons. 
Scales moderate, 130 to 180 cross series; no red on throat; mouth moderate; size 
very large (Montana, introduced) . . . . . . .  S. gairdneri Richardson. 
Scales always small usually in about 160 (150 to 200) cross series; nearly always a 
large deep red or scarlet dash on each side concealed below inner edge of each dentary 
bone; mouth large (native species) . . . . . oh Re ees 
5. Black spots almost as numerous on head as on See nae of body. 6. 
Black spots mainly on posterior part of body . . . 7. 
6. Black spots encroaching somewhat on belly (both slopes Ee ite Boar Mts. in Montana, 
IERERSIAUY 8. 08s: iden ee - |» » .» wd. Clark Richardson. 
Black spots not Eanes on belly (ications of Yellowstone Falls of Missouri R.) 
S. lewist Girard.1 
Fic. 6.—Salmo macdonaldi. 
7. Scales not very small, about 160 in lateral line; spots of moderate size (Species of 
Rio Grande Basin, Colorado and New Mexico) . . . . .  S. spilurus Cope. 
Scales very small; about 180 in lateral ine 6) 3) 
8. Spots rather large, lower fins distinctly red, rarely orange . . Q- 
Spots all small; lower fins bright yellow; a yellow lateral shade (Twin Lakes, Colo.) 
S. macdonaldi Jordan and Evermann.? 
g. Spots very numerous; a red lateral band (Colorado Basin; western slope in Colo.) 
S. pleuriticus Cope. 
Spots few and large, chiefly on the tail (Arkansas and Platte Rivers; Boulder Creek. 
Boulder, Nov. 1907, DeVoss and Perkins). . . aa ent S. stomias Cope. 
(Salmo jfario L., the European Brown Trout, has Boca introduced in Montana.) 
1o. Vomer with a raised crest; spotted with gray, without bright colors; D 11, A 11 
(Montana. (ey eee - + . . Cristivomer namaycush Walbaum, 
Vomer without raised crest; ed. Eat lower fins with bright edgings. rt. 
x “One of the present writers has caught them in the very act of going over Two-Ocean Pass from Pacific 
into Atlantic drainage’’ (JORDAN AND EVERMANN, American Food and Game Fishes, p. 170). 
2 A small Crustacean, Diaptomus judayi Marsh, is also confined to Twin Lakes, so far as is known. 
