242 The American Naturalist. [Mareh, 
the presence of a median horn on the extremities of the nasals, 
the presence of a sagittal crest? as indicated by the contour of 
the outer walls below this region and the presence of a strong 
anticrochet and crista and the absence of a well developed 
crochet on the superior true molars. 
The type consists of a portion of the skull and lower jaw. 
The superior and inferior molars are preserved and also the 
fourth upper premolar. The skull is long and proportion- 
ately much deeper and narrower than in the closely allied 
genus Aphelops. The nasals are only partially coossified, they 
are very thick and strong, much compressed anteriorly and 
strongly convex superiorly. Their extremities are prolonged 
into a short, stout horn which extends about an inch beyond 
the extremities of the nasals proper, and is directed upward 
and forward, it is slightly constricted inferiorly just in front 
of the termination of the nasals; it is rugose and in life evr- 
dently supported a dermal horn. These characters are well 
shown in Plate I, figs. 1, 1°, 1°, 1". The frontals are compar 
atively narrow and smooth, and their upper transverse surface 
is gently convex, they are elevated posteriorly so that the me- 
dian line from the posterior portion of the frontals to the end 
of the nasal horn is slightly concave. The infra-orbital fora- 
men is large, opens anteriorly and not laterally directly over 
the middle of premolar three. The maxillaries are larg® 
strong and deep. The anterior border of the posterior nares 
is on a line with the posterior border of the median sinus 0 
molar two, there is no median projection. The temporal re- 
gion is much constricted, the inferior lateral walls of the ga 
case in this region are exceedingly thin, there were no air ee 
ities in this region of the skull. The base of the skull sloped 
upward and forward from the condyles which are missing: 
The post-glenoid process is strong and triangular 10 ¢ 7 
tion, it is confluent but not coossified with the post-tympan 
throughout the greater portion of their length, thus entre 
enclosing the meatus auditorius externus. ; 
The lower jaw is exceedingly strong and massive. 4 
ascending portion is very high and broad with the poste o 
border but slightly expanded transversely. The masse 
