58 
BULLETIN OP THE UNITED STATES FISH COMMISSION. 
in hraehycephala , but they have been referred to the latter on account of the absence 
of a well-defined dark bar on the front of the femur, a color feature more or less 
characteristic of Western specimens. 
Museum 
No. 
Collector’s 
No. 
Locality. 
Date. 
17572 
17573 
80 
Beaverhead River, Dillon, Montana 
Swan River, near Swan Lake, Montana 
July 27 
Aug. 3 
6. Rana pretiosa B. & G. 
Of the fifty-six specimens all but five are from streams that empty into the Pacific. 
These five, Nos. 17574 to 17578, are from the junction of Firehole and Gibbon rivers, 
the headwaters of the Madison Fork of the Missouri. This fact is particularly inter- 
esting, inasmuch as I have been able to find but three other records of this species 
occurring in streams flowing to the east. One of these is noted by Prof. E. D. Cope, 
who found it in Prickly Pear Canon, just north of Helena, Montana. (Am. Nat., 1879, 
p. 435.) Another is a single Specimen, U. S. National Museum, No. 11503, collected 
at Fort Ellis, Montana, by W. B. Pratt; and the third record consists of two specimens, 
U. S. National Museum, Nos. 11937 and 11939, collected by C. Hart Merriam at “Upper 
Firehole Basin, Yellowstone Park.” In the list of specimens of Rana pretiosa belong- 
ing to the U. S. National Museum (see Cope’s Batrachia of North America, p. 434) there 
are apparently two more records of this species occurring east of the Bocky Mountains, 
but both are due to m ^identification, No. 3437, from the Bed Biver of the North, B. 
Kennicott, being R. septentrionalis , and No. 4824, St. Catharine, Canada, D. W. Beadle, 
R. sylvatica. It may possibly be owing in part to insufficient exploration that there 
are so few instances of this frog being found east of the Great Divide. 
In looking over this series, a very noticeable point is the lightening in color as the 
frog increases in age and size. The young is very dusky, the moss-agate-like dark 
dorsal spots being barely apparent, but as it grows the ground color pales, and while 
some of the black markings thus become more prominent, others fade entirely away. 
The largest specimen collected, No. 17603, a female from Deer Lodge Biver, Montana, 
is also the lightest colored. The ground color is very pale, rendering more conspicuous 
the few black dorsal blotches. The inferior dark markings are absent, and tire usual 
bars on the legs are broken up into several small spots. There is indication of a light 
median line on the back posteriorly. No. 17604, a smaller female from the same 
locality, is much darker, with all the usual markings, and the dorsal blotches more 
numerous. 
Four or five small specimens from Cottonwood Creek, Deer Lodge, Montana, show 
the darkest phase of the young very well, particularly No. 17593, a female, which has 
the black marbling of the throat finely marked, and all the spots on the sides and 
lower surface unusually distinct, while the upper ground color is so dark that the 
blotches on the back are hard to distinguish. No. 17591, a very slightly larger male, 
is almost as well marked. These differences in color are plainly not due to local 
causes, since dark and light come from the same locality; nor to sex, for dissection 
shows that the sexes are irregularly distributed among the varying shades of color. 
