160 BULLETIN OF THE 



Second cone on last upper molar united with the cingulum. Probably two 

 lower incisoi-s. Upper premolars with a faint or no internal cingulum. Nasal 

 bones intermediate in length and narrowing anteriorly. Horns elbngate, 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 fossae. Orbits rather small and 

 enclosed. A post-orbital process. Z^'^gomatic 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 froni M. Proutii, Leidy. In the Princeton collection is a 

 large skull which has been referred to this species. It differs from M. 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, aud of a strong 

 internal cingulum upon the premolars. 



M. dolichoceraa, sp. nov. This species may prove identical with S. acer. 

 Cope. Dentition: I. ?, C. ^, Pm. ^, 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 



