220 0. C. Marsh—New Tertiary Mammals. 
which start from the outer side, and meet in a prominent inner 
and slightly bifid tubercle. There are two low ridges outside 
of the main pair, which meet in the same tubercle. 
Measurements. 
Space occupied by first two upper molars,............+++ pen 
saree coetergs Auge of second aise molar,...+.-.--- i 
BR EUS NOD, os care eae ce oc sy ected ssaeese 2° 
Transverse diaiieeer’ of first upper molar,...........-.-- 1 
The above remains were DS last autumn, by the writer, 
near Henry’s Fork, Wyomi 
Scevuravus cee sp. nov. 
penultimate gle: and several isolated teeth. These remains 
indicate an animal about half the bulk of Seduravus undans 
Marsh. The lower incisor is more convex in front than in that 
species. The jaw is short and deep, and the masseteric fossa 
ends in front under the second molar. The wedge penultimate 
molar has three fangs, and the last one had four 
Measuremenis. i 
Space occupied by three posterior lower molars,.......-- ee gace 
Antero-posterior diameter of third lower molar,.......-++ 2° 
Altansverse diameter... 6.402 5 a 1°9 
epth of jaw below second lower ee Meee ee arg at 53 
Transverse diameter of lower in NOMWOE) eas va sok eae eee 1°2 
The remains at resent BS Uae this species were fo und, 
last autumn, at He and ay Buttes, Wyoming, 
by Mr. G. M. Keasbey and te write 
Colonymys celer, gen. et sp. nov. 
Another small rodent, about the size of the animal last de- 
scribed, is indicated by several isolated molars, which differ 
widely from the corresponding teeth in any genus of this group 
rom the Green River Tettiary deposits. A typical upper mo- 
lar in perfect condition has its crown composed of our princi: 
pal cusps, regularly arranged in two pairs. The outer pair are 
entirely separated from each other. The inner pair are very 
near together, and have their summits turned toward the center 
