432 THE VERTEBRATE SKELETON. 



species incisors also are absent. The dental formula is 

 . (02) 43 



^0=T) C (0=l)^4 m 3- 



Among the Titanotheriidae Palaeosyops 1 has very brachy- 

 dont teeth whose crowns have been described as buno-selenodont, 

 the inner pair of columns being bunodont, the outer, seleno- 

 dont. Similar grinding teeth occur in Chalicotherium. Some 

 of the Titanotheriidae have the regular mammalian series of 

 forty -four teeth. 



SUBUNGULATA. 



TOXODONTIA. Nesodon has the regular dental formula ; 

 its grinding teeth are rooted and the upper ones resemble those 

 of Rhinoceros. The second upper and third lower incisors 

 form ever-growing tusks. There is a marked difference between 

 the deciduous arid permanent dentition. Astrapotherium like- 

 wise has large rooted cheek teeth of a rhinocerotic type, and 

 each jaw bears a pair of permanently growing tusks, those 

 of the lower jaw being the canines. The dental formula is 



10 23 

 i -z c - pm - m , total 28. 

 o I L o 



In Toxodon the upper incisors and molars are large and curved 

 and all the teeth have persistent pulps. In Typotherium there 

 are no tusks, but the upper incisors are chisel-like, recalling 

 those of Rodents. 



The CONDYLARTHRA have brachydont, generally bunodont 

 teeth, with the premolars simpler than the molars. They 

 generally have the regular dental formula. 



HYRACOIDEA. The dental formula of Procavia is usually 



given as i^ c -pm-m-, total 34; in young individuals how- 

 ever there occur a second pair of upper incisors which early 

 fall out. The upper incisors resemble those of Rodents in 

 being long and curved and growing from persistent pulps. 



1 C. Earle, J. Ac. Philad., vol. ix., 1892, p. 267. 



