O. C. Marsh—New Tertiary Mammals. 249 
postorbital process on the frontal is longer than in Dicotyles, 
and more pointed. ere is a strong cingulum on the upper 
molars, excepting on the base of the inner cones. 
Measurements. 
Distance from fronto-nasal suture to ae on median line, 97:™™- 
Distance hese OFDIGS, OVER TONERS, 2 5c. 
Expan gomatic arches, Ee ee pee eer et 95 
Extent o of ae three upper m SAPs 
ee Seat ‘vs Pee aes ae molar, - ee? ie oe 14: 
‘Transverse diameter, (22. 722.5. 2. ee ones eae 14° 
Antero-poaterior diancier of second molar, ...-....-.-- 16° 
‘Transverse diameber,..02 22. es Gs a 14° 
Width between andiioe ry UM i oan woe ee 9° 
Antero-posterior a of auditory OL ee eee ee 24° 
Transverse diamete : seine 18° 
Length of sviapevie of lower j jaw (second specimen), . eer. 
Distance between lower canines, ESS esa 
Space between lower canines per first hanes wo ate EE 
Space between first and second lower premolars, ... --- 10° 
The present scat was somewhat larger than the Dicotyles 
torquatus. e remains here described are from the Miocene, 
of the John Day River, in Oregon. 
eee socialis, i nov. 
cellent preservation. In the present ks the last upper 
enamel of the upper molars is somewhat rugose, and there is a 
distinct basal vidoe except on the inner side. 
Measurements. 
Antero-posterior diameter of last upper molar, ..-.---.-  12°™™ 
Transverse diameter through anterior cones, ----- ----- 10° 
Transverse diameter through posterior cones, ---- -- ---- 8° 
Antero-poste terior diameter of second upper molar, - - .- - . - 12° 
Transverse —— id Pont, 555 12° 
Height of crown, 2. 0c be ace 6°5 
The type specimen of this species was cd in dete 
1871, in aes specimen beds of Oregon, by Mr. F. Mead, Jr., 
the Yale p arty. 
Eporeodon, gen. nov. 
Among the species now placed in the genus Oreodon of Leidy 
heck a: are ine well marked genera which may readily be pete 
guished by the base of the skull, and apparently by other char- 
