0. C. Marsh—New Tertiary Mammals. 241 
the series, much larger than the penultimate. The last lower 
see is smaller than the others. In the first and second true 
m , the external cusps are slightly in advance of the corre- 
apondtig inner ones. The nie pair are higher and nearer 
together than those behind. A low ridge extends os 
from the base of the anterior inner cone to the summit of the 
outer posterior cusp. The inner posterior cusp is satiate than 
the others, and separated from them. e crowns are bounded 
by a distinct basal ridge, ts on the inner side. The 
enamel of the molars is rugos 
Measurements. 
Space occupied by three lower true molars, .--..-------- = 
Antero- pomeae siapoeics of first lower molar, Guero see ‘ie 
Transverse diameter, - - - - - 6° 
Height of Grown. nc .nc5. 4 ee ee ee 5°5 
Antero-posterior diameter of penultimate Tica. te 5°5 
Transverse a ic cuva cue Uewae colt sme sere gree 5° 
eight’ of crowi. 602 226 Sei re Sera 4°2 
Depth of j sath haloes fivet lower molar, 0.5.5.5 77250 12°6 
This specimen was found in the Oreodon horizon of the Mio- 
cene ‘“‘ Bad Lands,” about thirty miles south of the Black Hills. 
Tillotherium fodiens, sp. nov. 
Since this genus was proposed by the writer (this Journal, 
v, p. 485, June, 1873), much light has been thrown upon its 
affinities by additional remains. It proves to be quite distinct 
from Ancheppodus(Trogosus) Leidy, although nearly related. The 
latter genus, unfortunately, is known only from portions of the 
lower jaw, but this shows marked differences from Tillotherium, 
which lacks the inner pair of small lower incisors, and has an 
incisor and a canine between the large sealpriform tooth and 
the first lower premolar. Tillotherium has 34 teeth in its per- 
manent dentition (p. 221), and the molar teeth most resemble 
those in Ungulates. The upper true molars are similar to the 
premolars of some Eocene Perissodactyls, but are somewhat like 
the tubercular molars of the Canide. The lower molar series 
is of the Paleotherium type and the last lower molar has a 
well developed posterior 
n the present species, the canines were small, and the su 
rior ones placed somewhat behind the Coad suture. he 
ve digits on each foot were all well developed, and of mode- 
= length. loo metapodial bones are similar to those in 
us, but the ungual phalanges preserved are more 
oblique; and less agciciith at the extremity. 
