20S LEIDY'S OSTEOLOGY OF THE HEAD OF HIPPOPOTAMUS. 



2. The head of a young female ? From the River Gambia. Presented by Dr. 

 S. M. E. Goheen to the Academy. 



In both jaws the first premolar is lost, but the alveolus remains. The second per- 

 manent premolar, in the upper jaw, is partially protruded, and entirely so in the lower 

 jaw. The third is partially protruded in the latter, but the second temporary premolar 

 had not been shed above. The temporary true molar remained in both jaws, but is lost 

 on one side. The anterior two permanent true molars are fully protruded, but the 

 last was but partially developed. The right intermaxillary bone is lost. 



Comparison of these heads of Hippopotamus amphihius, considered to he male and 

 female. — The upper part of the inion is much narrower, and forms a deeper notch 

 in the female than the male. The sagittal crest of the latter is three inches in length 

 from the inion to its bifurcation, and is formed by the conjunction of the temporal 

 ridges. In the female it is differently constituted, and this part of the cranium, in the 

 specimen under consideration, would not be much altered from any increase of age, 

 for the lambdoidal suture is obliterated. The summit of the occiput rises into a 

 prominent tuberosity, an inch in advance of the inion, which then abruptly declines 

 into a thin ridge, and after an inch more of length, bifurcates and diverges upon 

 the supra-orbitar processes. The temporal ridge proper is three-fourths of an inch 

 to the outside of the parietal ridge, is slight, and curves from the lateral occipital 

 crest forwards, to the bifurcation of the ridge last mentioned. 



The zygomse converge more rapidly forward in the male, and the orbits are 

 smaller, and present not so much upwards. The forehead is also slightly more 

 concave in the male, and the face considerably more so just in advance of the orbits. 



HIPPOPOTAMUS CAPENSIS, Desmoulins. 



Hippopotamus amphibius, p. auctorum: vide Fischer, Synopsis Mammalium, p. 

 424 ; Schinz, Syn. Mam. 2, 343. 



Hippopotamus Capensis, Desmoulins : N. Bull, des Sci. de la Soc. Philom., 1825 ; 

 Diet. CI. d'Hist. Nat., Hippopotamus. 



Hippopotamus australis, Duvernoy : Comptes Rend us, t. 23, p. 650. 



1. The head of an adult male. From the Cape of Good Hope. Deposited in the 

 Academy of Natural Sciences by Dr. Morton. 



The sutures of the face remain open, and the intermaxillaries have not co-ossified 

 with the maxillaries. 



All the permanent molars have fully protruded. The first premolar in both jaws 

 has been shed, and the alveolus filled up. The first true molars in both jaws have 

 had their enameled triturating surface obliterated. A hiatus of about an inch in 

 extent exists between the second and third premolars, in the upper and lower jaws. 



