xiii PHYLUM CHORDATA 455 



with the calcaneum. The brain-case is very small. Upper 

 incisors are sometimes wanting. Both upper and lower canines 

 are present, and the former are sometimes produced into elongated 

 tusks. The pre-molars and molars are of a simple and primitive 

 pattern. In some ( Uintatlierium and allies) the skull bears three 

 pairs of processes which may have been of the nature of horn- 

 cores. 



The Amblypoda comprise Corypliodon, Uintatherium, and other 

 Tertiary forms, both European and American. 



Sul-ordcr e. Toxodonta. 



Extinct Ungulates with massive skull, short, stout limbs, each 

 with three sub- equal digits. While the carpal bones interlock, the 

 tarsals are arranged in vertical series. The tibial articular surface 

 of the astragalus is nearly flat. The pre -molar and molar teeth 

 in Toxodon all grow from persistent pulps, in the other genera 

 the}* are rooted. 



This sub-order comprises Totodon and other genera from the 

 South American Tertiary beds. 



Sub-order f. Condyla rthra. 



Extinct (Eocene) Subungulata with usually five digits with 

 pointed terminal phalanges, in manus and pes, with an entepi- 

 condylar foramen and a third trochanter. The carpal and tarsal 

 bones do not interlock so completely as in the Ungulata vera. 

 The dentition is complete, and the teeth frequently exhibit resem- 

 blances to those of the Carnivora. 



This sub-order comprises Phenacodus, Periptyclms, and other 

 Eocene forms. 



A group of extinct Manuals, the Tillodontia, the affinities of 

 which are uncertain, may be mentioned here. They appear to 

 combine in a remarkable manner' Ungulate with Carnivorous and 

 Rodent features. 



ORDER 5. CARXIVORA. 



Mostly carnivorous Eutheria with furry integument, with never 

 less than four well-developed digits in each manus and pes, all 

 provided with claws which are frequently more or less retractile. 

 The pollex and hallux are never capable of being opposed to the 

 other digits. The clavicle is frequently absent, and, when present 

 is never complete. There is often a foramen over the inner con- 

 dyle of the humerus. The scaphoid and lunar of the carpus are 

 always united, and there is never an os centrale. 



They are diphyodont and heterodont, and the teeth are provided 

 with roots. The incisors, usually three pairs in the upper and three 

 in the lower jaw, are small and chisel-shaped. The canines are 



