486 O. C. Marsh—New Tertiary Mammals. 
The known remains of this species are all from the Eocene of 
Wyoming. : 
Brontotherium gigas, gen. et sp. nov. 
An examination of the remains, in the Yale Museum, of the 
uge mammals allied to Vitanotherium, has led to the discov- 
ery that two different animals have hitherto been referred to the 
species known as TZ: Prout. These animals are generically 
distinct, and probably are from separate geological horizons. 
The one here described differs from Titanotherium in its denti- 
tion, having but three lower premolars, the series being as fol- 
lows :—Incisors 2, canine 1, premolars 3, molars 8. The animal 
was, moreover, a true Perissodactyl, with limb-bones resembling 
those of Rhinoceros. The genus is related to Titanotherium™* 
and the two appear to form a distinct family, which may be 
called Brontotheride. oe 
The present species is based on portions of three individuals, 
one of which has the lower jaws and entire molar series com- 
plete. They indicate an animal fully equal to 7 Prout in 
size, and but little inferior in bulk to Ae Elephant. The lower 
molars resemble those in the type specimen of 7. Prouti, but 
the jaw below them is not so deep, and its lower margin is more 
nearly straight, descending but very slightly toward the angle. 
The front part of the lower jaws is somewhat suilline in form. 
The incisors are quite small, and the two next to the symphysis 
are separated from each other. There is a short diastema be- , 
bo 
and form interlocking series. The tail was long and slender. 
__* The generic name Titanotherium Leidy is antedated by Menodus Pomel (Bib. 
_ _Univ. de Genéve, x, p. 75, Jan., 1849). The latter, however, is ess ¢ Boe 
Same word as Menodon von Meyer, 1838, and is also objectionable in its ; 
