37 



Comparative Measurements of Head. 



Lower jaw of P. paludosus described from another speci- 

 men. 



The peculiar feature of this jaw is its remarkable exten- 

 sion back of the molar series (a feature which has not been 

 noticed heretofore), the distance from the last tooth to the 

 angle being greater than the length of the entire molar 

 series. From beneath the last molar, the lower margin 

 curves gently up to the symphysis. The alveolar border is 

 but slightly curved. Behind the last molar the lower mar- 

 gin forms a sigmoid curve, much more decided than in P. 

 major (first upwards and then downwards), and the ramus 

 thins out rapidly to the angle, where it has a slightly raised 

 border ; at the diastema the ramus curves outwards so as to 

 throw the canines out of the line of the molars. The sym- 

 physis is long. 



Dentition. The incisors, three in number, from length 

 and shape indicate a semicircular arrangement, as in most 

 Perissodactyles. They increase from first to third. The 

 crown of the first resembles very much that of the ruminants, 



