344 THE VERTEBRATE SKELETON. 



The teeth are always attached to the maxillae, premaxillae 

 and mandibles, never to any of the other bones. They are 

 nearly always implanted in distinct sockets, and are hardly ever 

 ankylosed to the bone. The teeth of mammals are generally 

 markedly heterodont, four forms, incisors, canines, premolars, 

 and molars, being commonly distinguishable. Some mammals 

 are monophyodont, having only a single set of teeth, but the 

 great majority are diphyodont, having two sets, a deciduous or 

 milk dentition, and a permanent dentition. 



The incisors, the front teeth, are simple, one-rooted, adapted 

 for cutting, and are nearly always borne by the premaxillae. 

 Next come the canines, one on each side in each jaw. They are 

 generally large teeth adapted for tearing or holding, and get 

 their name from the fact that they are largely developed in the 

 dog. The remaining teeth form the grinding series, the more 

 posterior of them, being the molars, which are not preceded by 

 milk teeth '. Between the molars and the canines are the pre- 

 molars, which do as a rule have milk or deciduous predecessors, 

 though very frequently the first of them is without a milk 

 predecessor. 



In describing the dentition of any mammal, for the sake of 

 brevity a formula is generally made use of. Thus, the typical 

 mammalian dentition is expressed by the formula 

 .31 4 3 11 

 *3 C T^4 m <ril' 



giving twenty-two teeth 011 each side, or forty-four altogether 2 . 

 The incisors are represented by i, the canines by c, the pre- 

 molars by p or pm, and the molars by m. The numbers above 

 the lines represent the teeth in the upper jaw, those below 



malleus ; according to Baur it forms the zygomatic process of the squa- 

 mosal, and according to Broom the interarticular mandibular cartilage. 



1 According to Leche, MorphoL Jahrb. xix. p. 502, the molar teeth 

 belong morphologically to the first series, i.e. they are milk teeth without 

 vertical successors. 



2 The researches of Bateson, P. Z. S. 1892, p. 102, have shown that 

 cases of individual variation in the number of teeth are common. 



