50 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
River, iu the southern peninsula of Michigan. The first-named locality, by the way, 
is one not generally known and not previously recorded. The occurrence of Grayling 
in the northern peninsula of Michigan is even disputed by anglers. 
The dilferences noted by Mr. Milner as distinguishing the Montana fish (as Tliy- 
mallus montanus Milner) do not seem to be constant. The Montana specimens are not 
deeper than the others (depth 5J), and in the number of the scales (98) they agree 
with the Otter Creek specimens. The Au Sable specimen has 93 scales. The dorsal 
rays are 21 or 22 iu Michigan specimens, 19 iu those from Montana. The only differ- 
ences evident are in the color of the dorsal fin. This is alike in all the Montana speci- 
mens, but its peculiarities may be due to difference of season. In the Montana ex- 
amples (in alcohol) the fin is largely dusky green. Its posterior part has three or four 
rows of bright orange-brown spots, faintly ocellated, irregular in position, some of the 
spots oblong and obliquely placed. Above this is one regular row of similar spots, 
extending obliquely across the fin from the end of the second third of the anterior rays 
to the tip of the last ray. Fin edged above with the same bright orange-brown. 
I have no specimens of the true northern signifer, but taking the figure published 
in the Natural History of Aquatic Animals, plate 195, as a basis of comparison, the 
grayling of Montana and Michigan may differ in the lower and less spotted dorsal and 
the slightly smaller scales (98 instead of about 92). Should these differences hold, it 
will stand as Thymallus signifer ontariensis (=T. tricolor Cope— T. montanus Milner). 
9. Salmo mykiss Walbaum. The Red-Throated or Rocky Mountaiu Trout. {Salmo purpuratus'Palla.S:-. 
Salmo stellatus, clarkei, virginalis, lewisi, etc., of authors). (Plate X, Figs. 10 aud 11.) 
I have compared a large series of trout from the Park with trout from various 
other streams in the Rocky Mountain region. There seems to be no doubt that all the 
trout iu the Park belong to a single species, and that this species is indentical with 
the common red-throated or black-spotted trout of the Lower Columbia, aud of the 
coast rivers from Oregon to Kamtschatka. This species was first mentioned by Steller 
under its Russian name of myldss. Later it received the binomial names — Salmo 
myhiss Walbaum, 1792, Salmo muikisi Bloch & Schneider, 1801, and Salmo purpuratus 
Pallas, 1811. Probably all the trout of the Rocky Mountain region belong to this sin- 
gle species, but certain marked varieties of it occur iu waters of Colorado, of which 
a detailed discussion is given in another paper. 
The trout of Yellowstone Lake seem to differ from those of Heart Lake and 
Henry’s Lake in having the black spots larger aud more distinct and rather less numer- 
ous. In these respects very much individual variation is shown. The trout from 
Heart Lake aud from Henry’s Lake are essentially like others from Walla Walla in 
this regard, and those from the Yellowstone below the falls have the spots generally 
smaller than in those from the lake. The trout of the Upper Missouri region have 
received the name of Salmo letcisi Girard, but I can not recognize S. leimsi as even 
varietally distinct from S. mykiss. In fact, as elsewhere stated in this paper, there is 
good reason to believe that the Yellowstone Lake was stocked originally from Snake 
River, through Pacific Creek, Two-Ocean Pass, and Atlantic Creek. It is, moreover, not 
unlikely that an interchange of individuals still occasionally takes place across the 
Continental Divide. 
The trout of the Yellowstone Lake and of many of its tributaries above the falls 
are infested by a parasitic worm {Dibothrium cordiceps Leidy). Of the specimens ex- 
