THE SKELETON IN MAMMALIA. THE SKULL. 467 



with cancellous bone, and above forms the floor of a long up- 

 wardly-directed auditory meatus. The mandible has a high 

 ascending portion and a small coronoid process (fig. 94, B, 13). 

 The hyoid differs from that of most Ungulates, the stylo-hyal 

 being very imperfectly ossified. 



In Hippopotamus the skull though essentially like that of 

 the pig is much modified in detail. The brain cavity is very 

 small, while the jaws are immensely developed. The face con- 

 tracts in front of the orbits and then expands again greatly, 

 to lodge the enormous incisor and canine teeth. The postorbital 

 bar is complete or nearly so, and the orbits project curiously 

 outwards and slightly upwards ; the lachrymal is thin and 



FIG. 95. MANDIBLE OF A HIPPOPOTAMUS (H. amphibius) x f . 

 (Camb. Mus.) 



The second incisor of the left side is missing and the crowns of the 

 grinding teeth are much worn. 



1. condyle. c. canine. 



2. coronoid process. pm 3. third premolar. 



3. mental foramina. m 1, m 3. first and third molar. 

 il, 1 2. first and second incisors. 



302 



