O. C. Marsh—New Tertiary Mammals. 128 
below at the suture, indicating a strong cartilaginous nasal 
septum. The anterior extremities are truncated, with the ex- 
ternal angles rounded. The upper teeth form a complete series. 
The canine is large, and broadly oval at its base. The outer 
incisor is the largest, and at its posterior edge the premaxillary 
18 subtriangular in transverse section. The sagittal and occi- 
pital crests are strongly developed, and the coronoid process of 
the lower jaw is short and recurved. The remaining portion of 
the skeleton, which will be described in detail in the full deserip- 
tion, shows conclusively that Paleosyops belongs to the Perisso- 
dactyls, and not to the Artiodactyl group of mammalia, as sup- 
posed by Dr. Leidy. 
Measurements. 
Length of entire upper molar series, 166 
Antero-posterior extent of three true upper molars, - --- - - 94° 
Antero-posterior diameter of last upper molar,.. _....--- 36° 
Transverse di We ay ok ee a ts 40° 
Antero-posterior diameter of upper canine at base,---.-- 29° 
; ransverse iameter, RSE ese sen Sele ek a aa a : 
“pace occupied by three right upper incisors, ..-.------- 34° 
Vertical extent of zygomatic process of squamosal,__.... 51° 
Transverse diameter of both nasals near anterior margin,. 42° 
Width between bases of tipper chnities son ost fool ct. 49° 
idth between bases of fourth upper premolars, - --- ---- 40° 
This unique specimen was discovered in September, 1870, 
by Mr. A. H. Ewing of the Yale exploring party. The locality 
was near Marsh’s Fork, about fifteen miles from Fort Bridger, 
Wyoming. The geological horizon was Eocene, or lower Mio- 
cene. Other specimens of the same species have since been 
found in the same region by members of both the expeditions. 
Telmatherium validus, gen. et sp. nov. 
A 
cated by the ‘greater portion of a skull with teeth, and portions 
of several other skeletons, obtained by the Yale party last year 
arsh,* is 
* This Journal, vol. ii, July, 1871, p. 35. Additional remains of this animal, 
~ ined during our explotsnoks inst “jeer, show clearly that it belongs to the 
a boscidea, as at first suspected. The species may therefore called Mastadon 
PO 
