mrropoTAMin.K 



279 



confined to the Old World. The dentition may be expressed by the 



The crowns of the molars (Fig. 100) 



formula i 



2—3 



. « T> P I> m §• 



1 4 

 1_3' > i' P 4' 



when worn present trefoil-shaped surfaces of dentine ; and those of 

 the premolars are sharp. The 

 facial portion of the skull is much 

 elongated, the orbits are tubular 

 and very prominent, and the man- 

 dible has a large rounded descend- 

 ing flange at its angle. The cars 

 are small, the tail is short, and the 

 legs are likewise so short that the 

 belly is raised but a little distance 

 above the ground. The brain is 

 not richly convoluted, and differs 

 very considerably from that of 

 the Pigs, approximating in some 

 respects to that of the Camel and 

 Giraffe, but on the whole standing very much by itself. The 

 stomach of the common species is of enormous dimensions, having 



Fig. 100.— Grinding surface of a worn molar 

 of Hippopotamus amphibius. (From Owen.) 



Fig. 101. — The Hippopotamus (Hippopotamus amphibius). 



an axial length of 11 feet, and measuring upwards of 15 feet along 

 the greater curvature. Its axis is longitudinal, the pylorus being- 

 situated almost in the pelvis, and it is divided into three distinct 

 compartments, of which the third is cylindrical. The liver of the 

 adult is of extremely simple form, elongated transversely, and narrow 

 from above downwards. "With the exception of a few tufts of 



