160 BULLETIN OF THE 
Second cone on last upper molar united with the cingulum. Probably two 
lower incisors. Upper premolars with a faint or no internal cingulum. Nasal 
bones intermediate in length and narrowing anteriorly. Horns elongate, sub- 
cylindrical in section at the base, and in side view inclined obliquely forward, 
so as to partly overhang the snout. Anterior nares transversely narrow and 
vertically deep, so that the snout is very elevated. Superciliary ridge promi- 
nent, rugose, and overhanging the temporal fosse. Orbits rather small and 
enclosed. A post-orbital process. Zygomatic arches wide and partly flanged. 
Post-glenoid and post-tympanic processes widely united. 
Description of Skull. — The type of this species is a single large skull, with 
the dentition complete, and lacking the upper part of the horns and the crest 
of the occiput. The total length is 29 inches, while Professor Cope’s type of 
S. altirostris measures but 25} inches. The separation from the latter species 
depends upon the number of lower incisors. Apart from size, the chief dis- 
tinction from M. Coloradensis is in the narrow and elevated terminal portion 
of the skull, giving a widely different appearance in front view. The zygo- 
matic arch is very massive, and presents a bulge in the posterior half, which 
however is much less prominent than in S. bucco, Cope. 
It is also distinct from MM. Proutii, Leidy. In the Princeton collection is a 
large skull which has been referred to this species. It differs from J. ticho- 
ceras in the presence of a diastema behind the superior canine, as well as in the 
presence of a distinct second cone upon the last upper molar, and of a strong 
internal cingulum upon the premolars. 
M. dolichoceras, sp. nov. This species may prove identical with S. acer, 
Cope. Dentition: I.?,C.1, Pm. 4, M%. Upper premolars with a faint in- 
ternal cingulum. Nasal bones extremely short and obtuse. Horns extremely 
long and powerful, directed obliquely forwards and outwards, projecting beyond 
the nasals in side view. The section is sub-oval at the base, with the long axis 
obliquely transverse. Cranium very broad and saddle-shaped above the orbits, 
narrowing somewhat posteriorly. A prominent and overhanging superciliary 
ridge. Post-glenoid and post-tympanic processes united for a short distance. 
The skull which we have made the type of this species is much larger and 
more powerful than Professor Cope’s type of S. acer. The horns are longer 
and more widely divergent at the base. The angle of inclination of the horns 
and the diminutive proportions of the nasals, as well as the form of the top of 
the cranium, all bring this specimen near S. acer, and separate it from other 
known species. Unlike S. acer, the horns are not united by a ridge. The 
specimen is incomplete in the supra-occipital region, the zygomatic arch is 
fragmentary, and the maxillary, palatine and basi-occipital regions are much 
distorted. 
M. platyceras, sp. nov. The type of this species is a pair of horns with 
the nasal bones attached. All other portions of the skull are wanting. 
The dentition is unknown. Nasal bones extremely short and obtuse, as in 
