332 A MANUAL OF DENTAL ANATOMY. 



pattern becomes obliterated, and a plain field of dentine 

 surrounded by enamel alone remains. 



The teeth of the Hippopotamus are subject to a great 

 amount of attrition, as is well shown by a specimen pre- 

 sented to the museum of the Odontological Society, in which 

 the molar teeth are all excessively worn. The Hippopotami 

 use their incisors and canine tusks for the purpose of up- 

 rooting aquatic plants, of which their food mainly consists : 

 the roots of these are of course mixed up with much sand, 

 which wears down the teeth with great rapidity. The larger 

 incisors and the canines are, and for centuries have been, 

 articles of commerce, the ivory being of very dense substance 

 and useful for the manufacture of small objects. 



Anoplotherici.se are an extinct (Eocene and Miocene) 

 family, linking together the Pigs and the Pecora. 



Fio. 142 (i). 



Anoplotherium is a genus of interest to the odontologist 

 because fc it possessed the full typical mammalian dentition, 

 as far as the number of the teeth went; the teeth were 

 of nearly uniform height, none strongly differentiated from 

 those nearest to them ; and they were set in close contiguity 

 with one another, so that there was no " diastema." 



The lower molar teeth of the anoplotherium are built up 



J ) Side view of the dentition of Anoplotherium (after Owen). 



