136 On a new Tuco-tuco from Bolivia. 
X.—A new Tuco-tuco from Bolivia. 
By OLDFIELD ‘THOMAS. 
(Published by permission of the Trustees of the British Museum.) 
AMONG some mammals from Eastern Bolivia presented to the 
National Museum by Mr. Walter Goodfellow there occurs a 
large tuco-tuceo allied to the Clenomys boliviensis of Water- 
house, from Santa Cruz de la Sierra, but sufficiently different 
in its cranial characters to deserve distinction. 
Ctenomys boliviensis is represented in the Museem by two 
cotypes, and of these I propose to select the mule (B.M. 
no. 46. 7. 28. 57), of which the skull was figured by 
Waterhouse, as the lectotype. 
The new form may be called 
Ctenomys goodfellowi, sp. n. 
Size slightly less than in boliviensis. Colours essentially 
the same, though the dark dorsal line is heavier and the white 
of the under surface is reduced to inconspicuous axillary and 
inguinal patches. 
Skull, as compared with that of the lectotype of boliviensis, 
equally an adult male, rather smaller and less heavily ridged, 
even though, judging by the basilar suture, it is rather older. 
Sides of muzzle with the same peculiar bony thickening 
characteristic of bdoliviensis, and figured by Waterhouse. 
Nasals shorter and less broadened anteriorly, consequently 
more nearly parallel-sided. Interorbital space broader, its 
margins forming nearly parallel-sided overhanging ledges, 
instead of the abruptly developed postorbital processes found 
in boliviensis with deep lateral orbital concavities in front of 
them. Zygomata not so greatly thickened, the suborbital 
part with a deep crescentic cleft on its upper side, represented 
in boliviensis merely by a shallow concavity. Orbital fossa 
much shorter, so that the ascending malar process is almost 
exactly at the centre of the combined orbito-temporal fossa, 
instead of, as in bolivtensis, much nearer its hinder end. 
Palation level with the middle of m*. Bulls smaller and less 
inflated than in boliviensis, with the meatal tube unusually 
elongated. As in boliviensis, the incisors are very broad and 
heavy, with orange fronts, and the premolars are very large. 
