CHAPTER XI 



ASTRAPOTHERIA 



This group is composed of large, long limbed creatures, 

 with a highly specialized dentition, in which the canines 

 of the upper jaw are developed into great curved tushes, 

 resembling those of Pyrotherium; while the canines of the 

 lower jaw are compressed in the antero-posterior diameter 

 and protrude laterally, like those of pigs. Upper pre- 

 molars I and 2 are reduced or lacking, while pm. 3 and 4 

 are also reduced, but usually retained. The upper molars 

 are brachydont, and have a crown very like that of the 

 molars of homalodontotheres. 



The lower incisors are small, proclivious, and set at 

 intervals around the broad semicircle of the front of the 

 fused lower jaws. The lower canines are permanently 

 growing teeth, smaller than the upper canines, project 

 laterally, and have the tips recurved. Premolars 1 and 

 2 are usually lacking, pm. 3 more or less reduced, and pm. 

 4 is a normal, short, molariform grinder. The lower 

 molars have the same basal pattern as in Toxodonta, 

 the crown carrying two crescents with a plump pillar in 

 the basin of the posterior crescent, the pillar, however, 

 being situated far forward near the anterior horn of the 

 rear crescent. 



Lydekker made an order A sir a pother ia including the 

 Astrapotheria and Homalodontotheria, but as the dentition 

 of the two groups is so different, because of the enormous 

 enlargement of the frontal region, and because of the 

 reduction of the premolars, I am convinced that these 

 two groups represent totally divergent lines of develop- 

 ment; and I have therefore made each of the groups a 

 separate suborder. 



