Mil 



PHVLIM CHORDATA 



5(>5 



first upper prc-inolar is nlniost always without, a milk predecessor. 

 The P i.^ (Fi,ty. 1192) arc anioug the very few recent Mammalia 



Fio. 1192.— Left lateral view of the dentition of 'tlio Boar'<S!(.s scrofa), tlie roots of the teeth 

 being exposed. (After Flower and Lydekker.) 



which possess what has been referred to as a typical dentition : the 

 formula of the completed dentition is — 



.31 4 3 .. 



The incisors of the upper jaw are vertical, those of the lower 

 greatly inclined forwards. The canines are greatly developed, 

 especially in the male, and grow from persistent pulps ; both the 

 upper and lower are bent upwards and outwards and work 

 against one another in such a manner that the upper wears on its 

 anterior and external surface, the lower at the extremity of the 

 posterior. The pre-molars are com]3ressed, with longitudinal 

 cutting edges, and the molars provided with numerous tubercles 

 or cusjDS arranged for the most part in transverse rows (bunodont 

 type). The formula of the milk dentition is — 



i.|.4,m.| = 28. 



In the typical Ruminants there are no teeth on the premaxillse, 

 the incisors of the lower jaw and the canines, which resemble them 

 in shape, biting against a thickened callous pad on the opposed 

 surface of the upper jaw, and the upper canines are also usually 

 absent ; there are three pre-molars and three molars in both upper 

 and lower series, all characterised by the presence of column-like 



