On a new Frog from Upper Burma and Siam. 219 
Two specimens are in Major Delmé Radecliffe’s collection, 
and | have examined a third (a young), also from the Victoria 
Nyanza, forming part of a small series of fishes purchased by 
the British Museum from Mr. Baxter in 1894. This young 
specimen had been provisionally referred by Dr. Giinther to 
his M. shiranus, which differs in having fewer dorsal spines 
and soft fin-rays. 
XV.— On a new Frog from Upper Burma and Siam. 
By G. A. BouLencer, F.R.S. 
TEN years ago, when describing the Batrachians collected in 
Upper Burma by the late Signor L. Fea*, I noticed the 
characters of some frogs from Yado and Thao, Karin Hills, 
which I took to be males of Rana Guentheri, Blgr., a species 
established upon female specimens from Amoy, China. 
Having recently had the opportunity of examining a good 
series of specimens of Rana Guenthert from Annam and 
Tonkin, I have discovered my error in the determination of 
the male frogs from Yado and Thao, the males of R. Guen- 
thert being provided with large external vocal vesicles on the 
sides of the throat as well as with a humeral gland. The 
allied frog, in which the vocal sacs are internal, is an un- 
described species, and as I have lately had further specimens. 
for examination, collected by Dr. Mortensen on Koh Chang 
Island, in Siam, for the Copenhagen Museum, I cannot do 
better than propose for it the name of 
Rana Mortensen. 
This species is closely related to Rh. Guwenthert, but differs 
in the more posterior position of the vomerine teeth, which 
form two oblique series or oval groups beginning in the 
middle between the choanze and extending posteriorly more or 
less beyond them, in the shorter snout, in the shorter foot, in 
the larger terminal expansions of the toes, and in the thicker 
and more prominent dorso-lateral glandular fold. 
In coloration the two species are very similar, but 2. Guen- 
thert has a more or less distinct whitish posterior border to 
the tympanum, which does not exist in 2. Mortensent. 
* Ann, Mus. Genoya, (2) xiii. (1893). 
