1372 



CLASS MAMMALIA. 



Fig. 1247.— The third right upper true 

 molar of Chalicotherutm sinense ; from 

 the Pliocene of China. 



V-shaped surfaces of dentine appear on the crown. This type of 

 tooth may be derived from the Lophodont by the more or less 

 complete abortion of the middle portions of the transverse ridges. 

 The upper premolars are simpler than the true molars, and have 

 but a single inner column ; while the lower cheek-teeth are crescen- 

 toid, the last true molar usually not having a complete third lobe. 



There was always a diastema in the 

 dental series, and the skull was de- 

 void of bony protuberances. In 

 the present North American family 

 the femur has a third trochanter, and 

 the feet are of the normal Perisso- 

 dactylate type, the manus being pro- 

 vided with four, and the pes with 

 three digits. This family is repre- 

 sented by Palceosyops and Limno- 

 therium, from the Upper Eocene, in 

 which there are four premolars, and 

 the last lower true molar has a third 

 lobe ; the canines being large and 

 resembling those of the Carnivora. 

 Lambdotherium is another form of 

 later age ; while in the White-river Miocene of Canada we have 

 Haplacodon, with only two pairs of lower incisors. 



Family Chalicotheriid.e. — The second family, or Chalico- 

 theriidce, is found in both the Old and the New Worlds, and pre- 

 sents such a remarkable abnormality in the structure of the feet, 

 as to render it for the future quite unsafe to predict the character 

 of an animal from a single bone, and to make invalid the old 



maxim ex ungue leonem. In 

 the femur the third tro- 

 chanter has been lost; and 

 in the feet, while the proxi- 

 mal bones retain their normal 

 Perissodactylate character, 

 the phalangeals have been 

 modified to resemble those 

 of Edentates, the second 

 phalangeal (fig. 1248) hav- 

 ing a strongly developed dis- 

 tal trochlea for the articula- 

 tion of the huge claw forming the terminal joint. These phalan- 

 geals have been described under the names of Macrotherium 

 and Ancylotkerium, and were until quite recently, when they were 

 found by Dr Filhol in association with the skull and the rest 



Fig. 1248.— Anterior and distal aspects of a second 

 phalangeal of Ckalicotherium sivalense ; from the 

 Siwaliks. 



