374 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Body between lateral folds varying from almost unicolor to definitely 
marked with darker. Lateral folds, if present, light and bordered 
by a line of dark spots, the sipots sometimes forming a streak. Sides 
generally heavily marked. 
Fore legs. A dark mark on anterior edge of humerus, and 
otherwise spotted lightly and irregularly. 
Ilind legs. Faintly barred, but generally spotted with darker. 
Ventral surfaces. Pale white. Faint and almost no dusky 
markings. The distribution of this species covers the greater part 
of Alaska, and extends southward to the region of Great Slave 
Lake, Can. 
Cope, Bull. 34, IT. S. nat. mus., 1889, recognized a color variety, 
Rana cantabrigensis evittata , but this owing to the great insta¬ 
bility of coloration common to wood frogs cannot stand. The 
diagnostic character he mentions in addition to coloration, viz: 
“ three phalanges free,” I find on looking over a series of speci¬ 
mens does not hold; and Cope could not have had a very clear idea 
of the form himself when he identified with it a specimen from 
Moose River, Can. (5366), whereas this specimen is without doubt 
Rana septentrionalis Baird. 
In examining a large series of wood frogs it becomes at once evi¬ 
dent that the only stable character that can be followed for identi¬ 
fication is the comparison of measurements; the most important 
being the comparison of the length of the tibia to the body. The 
following table shows how distinctly these measurements separate 
the two species and subspecies. 
Rana silvatica. Tibia more than half the length of the body. 
Rana cantabrigensis. Tibia one half the length of the body. 
Rana cantabrigensis latiremis. Tibia less than one half the 
length of the body. 
The distribution also, to a great extent, separates the three. 
In preparing these descriptions alcoholic specimens in the case of 
R. cantabrigensis and its subspecies have been used and an allow¬ 
ance for faded coloration should be made, although some consider¬ 
ation was taken of this fact when writing the descriptions. 
I take this opportunity to thank Mr. S. Garman and Mr. G. M. 
Allen for their great kindness in helping me in many ways in the 
preparation of this paper, and also Mr. F. W. True for his kindness 
in forwarding me specimens from the United States national 
museum. 
Printed February, 1899. 
