58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 6l 



i 



PLATE 12 

 (About r /s natural size) 

 Illustrating generic characters 



Fig. i. Rhinoceros unicornis, immature; milk molars in use; permanent 

 incisors just erupting; from the menagerie of Barnum and Bailey; 

 sex and origin unknown. No. 16251, U. S. National Museum. 



Dorsal outline deeply concave; incisors in both jaws; post- 

 glenoid and post-tympanic processes united. 



Fig. 2. Dicer os bicornis, male, old; Loita Plains, Southern Guaso Njoro Dis- 

 trict, British East Africa; shot by Col. Theodore Roosevelt, 

 June 18, 1909. No. 162830, U. S. National Museum. 



Occipital crests produced above dorsal plane of skull but not 

 beyond the condyles ; post-glenoid and post-tympanic processes 

 separated. 



Fig. 3. Ceratotherium simum cottoni, female, old; from Rhino Camp, Lado 

 Enclave; weathered skull. No. 164597, U. S. National Museum. 



Nasals and premaxillse widely separated ; dorsal profile of skull 

 showing very slight deflection of the occipital crests, but the latter 

 greatly produced backward beyond condyles; post-glenoid and 

 post-tympanic processes separated. 



Fig. 4. Coelodonta antiquitatis, adult; from the Pleistocene of the Tunguska 

 River, Siberia. No. 6053, U. S. National Museum. 



Mesethmoid greatly developed and united with the nasals ; nasals 

 and premaxillae united at their tips into a solid rostrum ; occipital 

 crests inflected upward above dorsal plane of skull; post-glenoid 

 and post-tympanic processes united. 



