XIII 



PHYLUM CIK )RDATA 



565 



first upper prc-molav is almost alwaj's without a milk predecessor. 

 The Pigs (Fig. 1192) are among the very few recent Mammalia 



Fin. 1102.— Left lateral view of the doutition of -the Boar'(.S('.i .^'-roh'), the roots of the teeth 

 being exposed. (After Flower and Lydeltker. ) 



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

 formula of the completed dentition is — 



4 



4' 



44. 



The incisors of the upper 

 greatly inclined forwards, 

 especially in the male, and 



jaw are vertical, those of the lower 

 The canines are greatly developed, 

 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 uppjer wears on its 

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

 posterior. The pre-molars are compressed, with longitudinal 

 cutting edges, and the molars provided with numerous tubercles 

 or cusps an-anged for the most part in transverse rows (bunodont 

 type). The formula of the milk dentition is — 



• 3 1 8 ^^ 



I - c. -, VI. - = 28. 

 3 1 3 



In the typical Ruminants there are no teeth on the premaxilla;, 

 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 



