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MUSEUM OF COMPARATIVE ZOOLOGY. 157 
collection the well-preserved facial part of a skull, together with the lower 
jaws ; hardly enough, however, to make the systematic position of the animal 
entirely clear. The orbits are very large and deep-set, as in the tragulines, 
and separated by a mere septum ; the lachrymals have a considerable extent 
vertically, but extend little on the side of the face, and do not reach the nasals; 
the maxillaries are proportionately higher than in Leptomeryz ; the nasals are 
much contracted ; the palate is well arched from side to side, and the palatines 
seem to be shaped much as in Tragulus ; the mandible is very slender. 
The last upper premolar is composed of an external and internal crescent, 
enclosing a valley between them ; the third and second are very small and 
apparently secant, without internal cusps ; the first, if present at all, was evi- 
dently separated from the second by a considerable diastema. 
-  PERISSODACTYLA. 
MENODONTIDA. 
MENODUS, PoMELt. 
Syn. Titanotherium, Leidy. Megacerops, Leidy. Brontotherium, Marsh. (? Sym- 
borodon, Cope.) Diconodon, Marsh. 
Generic Characters. — Dentition: I. 2 (variable), C. 1, Pm. 4, M. 8. The 
incisors are small and variable in number. The upper and lower median in- 
cisors are usually wanting. Molars and premolars alike, resembling those of 
Chalicotherium in pattern. A stout pair of transversely placed horns devel- 
oped from the frontals and nasals. 
There are three skulls in this collection and the horns of several others, rep- 
resenting four or five species which may readily be distinguished. The chief 
difficulty is in deciding where to draw the generic lines, which is increased by 
the fact that the mandibles are seldom found associated with the skulls. As 
in Uintatherivm, the variability in the various portions of the skull, especially 
in the region of the horns, is so extreme, that no two skulls are found which 
are exactly alike. But the dentition, which is constant among the Dinocerata, 
here greatly complicates the problems of classification. The premolars vary in 
number, and the incisors, always of relatively small size, and fairly constant 
in number in the upper jaw, vary from three to none in the lower jaw.* In 
all the lower jaws found in Professor Cope’s collection of Menodontide from 
Northern Colorado there are no incisors, and the mandibular symphysis is 
extremely narrow. In the lower jaws of the Cambridge and Princeton collec- 
tions, which are all from the Nebraska and Dakota exposures, the symphysis 
is broad, and the incisors where preserved are two in number, while in one of 
the Cambridge specimens no less than three incisor alveoli may be counted 
upon one side of tlie symphysis. 
* One of the Cambridge skulls has but a single upper incisor, MZ. coloradensis. 
