PETERSON: THE AMERICAN DICERATHERES. 415 



Specific Characters. — Diceratherium armatum may he characterized as follows: 

 Frontals relatively broad over the orbits. Sagittal crest short. Inion light. Broad and 

 heavy nasals. Anterior nares not extended as far back of the horn-cores as in D. 

 cooki. Muzzle and ijremaxillaries long. Postglenoid and paroccipital processes 

 well separated. Cheek-teeth comparatively simple in the configuration of their crowns. 

 Animals of larger size than tapirs. [?Median lower incisors proportionally large.]* 



General Description. — As stated above, the type specimen of this species is 

 somewhat depressed by crushing. In the Peabody Museum collection is an 

 additional specimen, a skull with fragments of the lower jaws, re-identified by 

 Professor F. B. Loomis. This second specimen has the contour of the top much 

 better preserved. From these two specimens it is at once observed that the fron- 

 tals are quite broad over the eyes, which causes a rather short, sharp, emargination 

 of the muzzle back of the horn-cores. The latter are, as in D. niobrarense, located 

 near the lateral border of the nasals; they are well developed though somswhat 

 less in proportion to those in D. annectens of the same horizon. The nasals as a 

 whole are, however, heavier than in the later forms from Nebraska, D. niobrarense 

 and D. cooki, while one might look for evidence to the contrary. Even when the 

 crushed condition of the John Day type is duly considered, it seems clear that the 

 nasals were not elevated over the premaxillaries as high as in the later Diceratheres 

 from Nebraska. The temporal ridges are rather weak and the sagittal crest is 

 not greatly developed and occupies a smaller antero-posterior area than in D. 

 niobrarense. The inion is not nearly as heavy as in the latter form, resulting in 

 a comparatively less saddle-shaped top. The nasals are unfortunately broken off 

 in front of the horn-cores, but enough is present to indicate that they were of con- 

 siderable length and possibly terminated in a rather sharp point. The premaxil- 

 laries are also broken off, but what remain of them indicates that they were of 

 greater length than in the Nebraskan species. There is present a heavy lachrymal 

 process in D. armatum. The palate is broad as are also the posterior nares. The 

 anterior margin of the posterior nares extends even with the anterior face of M-. 

 The post-glenoid and paroccipital processes are well separated, indicating the 

 condition found in earlier Rhinoceroses. That the alveolar border of the maxil- 

 lary terminates more abruptly back of M' and the paroccipital process is less 

 robust than in some of the Nebraskan species are perhaps characters of less im- 

 portance. 



The dentition of the type is perhaps better known than any other part of the 



* The only lower jaw of a large species with median incisors present is D. tmquianum Cope. If 

 the latter species should prove to be identical with D. armatum Marsh, then the above specific character 

 is valid. 



