418 



MEMOIRS OF THE CARNEGIE MUSEUM. 



Specific Characters. — Premaxillaries long and slender. Nasals and nasal horn- 

 cores of males broad and heavy. Muzzle long. Anterior nares excavated back of the horn- 

 cores in the same proportion as in D. armatum. A well-defined and quite heavy sagittal 

 crest. Occiput overhanging, and the cranium well extended back of the posterior angle 

 of the zygomatic arches. Liberal separation between the postglenoid and paroccipital 

 processes. First premolar relatively large. Cheek-teeth with swollen cross-crests 

 and crowns otherwise complicated; crista and crochet present, especially on the pos- 

 terior premolars and the molar series. Median and lower incisors proportionally 

 large. Animal about the size of, or larger than, a tapir. 



General Description of the Type Material. 

 From recent studies of the type material of Professor Marsh's collection in 

 the Peabody Museum and the splendidly preserved skull in the Cope Collection of 

 the American Museum there is now no valid reason for regarding the types of 



Fig. 11. Diceratherium anncctcns (Marsh)- No. 10001, Coll. I'imK.mIv Museum of Natural History. 

 Premolar teeth of left side and superior incisor. X 5. 



D. annectens and D. nanum as belonging to separate species. D. annectens, having 

 been described before D. nanum, and also being now found to possess sufficient 

 characters for identification and comparison, must be regarded as the type. 



In his description of D. annectens Professor Marsh was apparently not entirely 

 clear as to the composition of the specimen. Professor Loomis correctly associates 

 the type, but mistook some of the premolars for molars. 



There is no doubt in the mind of the present writer that this series of pre- 

 molars belongs to one individual. In placing the teeth together one finds that 

 they fit against one another perfectly and the grinding surfaces form a natural 

 gradation generally obtained in specimens of D. cooki which have reached an equal 

 stage of wear. Whether or not the associated incisor tooth belongs to the type 

 is less satisfactorily determined, as it has received comparatively little wear and 

 appears small in proportion. The small amount of wear of the upper incisors 

 is, however, often found in skulls of D. cooki, when the cheek-teeth have been well 

 ground down. 



