from North-western Patagonia: 201 
JRENOMYS *, gen. nov. 
General facies as in Oryzomys. Upper incisors grooved. 
Molars hypsodont, laminate, the lamin lozenge-shaped in 
section. 
Genotype. I. longicaudatus (Retthrodon longicaudatus, 
Eshib.j). 
The skull, judging by an immature example, is on the 
whole not unlike that of Phyllotis, and presents no very 
special peculiarities. The interparietal is of full size. The 
zygomatic plate is of average breadth, but little projected 
forward, not undercut. Palatine foramina long, penetrating 
between the molars. The internal pterygoids, however, are 
unusually thickened, flattened, and turned outwards above, 
though this may be partly due to immaturity. Bulle of 
medium size. 
Upper incisors with a sharply defined groove. 
Molars very peculiar, hypsodont, laminate, with three 
laminze to m1, two to m? and m*®, and the same numbers in 
the three molars below. The lamine of the upper teeth are 
very much as if the re-entrant angles of each side in the teeth 
of Phyllotis penetrated further into the teeth, so as to cut 
connection between the dentine spaces of each lamina, while 
still leaving the laminz lozenge-shaped and just touching 
each other at these median points. As a result, the shape in 
section of the laminee in a young animal is almost precisely 
similar to that in the African elephant, as viewed vertically, 
though of course the spaces between the lamina are not filled 
up with cement. Such teeth as these would in old age wear 
down to a sufficient approximation to Philippi’s figure to 
render it certain that the two animals are congeneric, 
This new genus is undoubtedly quite distinct from any 
previously recognized, and it is not easy to be certain as to 
its relationship to others. Probably it is most nearly allied 
to Phyllotis, of which it may be looked upon as a relative 
with grooved incisors and simplified molars. But, in any 
case, the difference is very considerable, and the study of 
adult specimens may cause some modification of this opinion. 
Sr. Budin noticed that the single specimen was distinct 
from the ordinary Oryzomys, to which it has so marked a 
resemblance, and did all in his power to get further examples, 
but without success. 
“Caught among the roots of fallen trees, like all the other 
species of the Beatriz peninsula.”—/. B. 
* So named as a memento that its recognition coincided with the 
arrival of a glorious peace. 
+ An, Mus. Nat. Chile, pt. 14, “ Muridee of Chile,” p. 64 (1900). 
