DESCRIPTION OF A NEW SPECIES OF HIPPOPOTAMUS 



By GERRIT S. MILLER, Jr., 

 . Curator, Division of Mammals, U. S. National Museum 



(With Four Plates) 



Two skulls of Hippopotamus in the U. S. National Museum, one 

 from the Zambezi River, the other from Angola, differ noticeably 

 from each other in important details of form. Hitherto the exact 

 value of these characters could not be determined, owing to lack of 

 material to illustrate the normal variation in individuals from one 

 locality. The series of eight skulls from British East Africa col- 

 lected by the Smithsonian African Expedition shows conclusively 

 that individual variation in this genus is not unusually great, and 

 that the Zambezian and Angolan specimens must be regarded as 

 representing distinct species. In all essential characters the Zam- 

 bezian skull agrees with those from British East Africa; these are 

 for the present assumed to represent true Hippopotaimis arnphibius 

 of the upper Nile.^ The Angolan animal may be known as : 



HIPPOPOTAMUS CONSTRICTUS, sp. nov. 



Type. — Skull of immature male (m^ not fully in place), number 

 34787, U. S. National Museum ; collected in Angola, Africa, by H. 

 Chatelain. 



Diagnosis. — Skull in general like that of Hippopotamus arnphibius, 

 but rostral constriction deeper, dorsal surface of cranium more flat- 

 tened, difference in level between anterior border of maxillary and 

 of premaxillary more pronounced, and mandibular symphysis much 

 shorter, its median length less than one-third length of mandible; 

 teeth smaller than in Hippopotamus arnphibius, the transverse diam- 

 eter of m^ scarcely more than one-half that of palate. 



Skull. — The skull is throughout less robust than that of Hippo- 

 potamus arnphibius, a peculiarity equally noticeable in dorsal, ven- 

 tral, or lateral aspect; depth at level of anterior border of orbit 

 contained about 4 times in condylobasal length, instead of 3>4 times, 

 as in H. arnphibius; rostral constriction very pronounced, its least 



*This paper is the seventh dealing witli the results of the Smithsonian 

 African Expedition. 



Smithsonian Miscellaneous Collections, Vol. 54, No. 7 



