DINOCEEATA, TILLODONTIA, AND TOXODONTIA. 



In the group of the Stylinodontidae, besides Stylinodon itself, 

 we have the genus Dryptodon, in which the dental formula is, 



.3—3 



1—1 

 1—1 



pm 



3o ' 



O 1 



3—3 



3—^ 



40. 



Of the six incisors in each jaw, the four central ones are 

 small, but the outermost ones are huge and compressed, faced 

 with enamel, and growing from persistent pulps. The molars 

 and prsemolars are rootless and cylindrical ; and the canines 

 are small. 



Order IX. Toxodontia. — This order includes certain large 

 extinct Mammals from the later Tertiary deposits of South 

 America, the true systematic position of which is still very 

 doubtful ; since they present affinities to the Ungulata, the 

 Eodents, and the Edentates. The skull is massive and the 

 dentition is very peculiar. The molars and premolars are 

 bent so as to be strongly convex outwards and concave in- 

 wards, with flat grinding surfaces (fig. 659), and presenting 

 the peculiarity that they are rootless and grow from per- 



Fi". 659. — A, Eight upper jaw of Toxodon Burmeisteri, and b, left lower jaw of the same ; 

 c, Lower canine. (After Burmeister. ) Greatly reduced in size. 



sistent pulps. Canines are present in the lower jaw, but are 

 of very small size (fig. 65 9, c) and are placed in the interval 

 between the incisors and prsemolars. In the upper jaw only 

 the sockets for the canines are left. There are four upper 

 and six lower incisors, which are separated by a wide dias- 

 tema from the pra?molars. The dental formula is — 



0- 



3—3 



-0 4—4 



-1 3—3 



= 38. 



