CARNIVORA. 381 



bones both of the carpus and tarsus are perhaps more distinctly 

 interlocking than those of the Condylarthra. The expanded 

 upper portion (head) of the astragalus, with its gently 

 sinuous surface for the articulation of the tibia and fibula, 

 is fixed obliquely upon the small lower portion (neck), which 

 articulates not only with the navicular but also with the 

 cuboid. The scaphoid and lunar of the carpus only rarely 

 fuse together. 



The known Creodonta range from the base of the Eocene 

 to the Lower Miocene both in Europe and North America, and 

 are especially abundant in the rocks of the latter area. There 

 is also some evidence of the same group in the Lower Tertiaries 

 of Patagonia. The more specialized forms exhibit a dentition 

 remarkably similar to that of the existing carnivorous mar- 

 supials of Australia; but the series of successional teeth is 

 proved in some cases (Hycenodon, Pterodon, Thereutherium, and 

 Triisodon) to have been nearly or quite complete, as in ordinary 

 placentals. The known generic types are also so varied that 

 the different groups of true Carnivora are assumed to have 

 already begun to diverge before the creodont grade had been 

 passed. 



Arctocyon. The typically omnivorous bear-like forms are represented, 

 among other genera, by Arctocyon, which is known by a large part of the 

 skeleton. The small elongated cranial region of the skull is surmounted 

 by a great sagittal crest, and the zygomatic arch is both very massive and 

 strongly bent outwards ; the facial region is small and slender. The 

 cranial cavity exhibits an unusually large development of the olfactory 

 lobes, and the impression of the cerebral hemispheres shows them to have 

 been nearly smooth. The mandible bears a much-elevated coronoid process. 

 The dental series is complete or nearly so, namely, with three incisors, one 

 canine, three or four premolars, and three molars in each jaw. All the 

 molars and premolars exhibit a prominent cingulum at the base of the 

 crown, which sometimes bears small tubercles; the canines are well 

 developed, acutely pointed, and with a sharp cutting edge along the hinder 

 concave border. Upper molars 1 and 2 are nearly square in shape, while 

 no. 3 is smaller and more rounded; and the grinding surface is tuber- 

 culated like that of the bears. Upper premolar 4 is tritubercular, while 

 premolars 1 to 3 are relatively small and simply conical. The lower 

 molars much resemble those of the upper jaw but are antero-posteriorly 

 elongated ; the lower premolars are simply conical and laterally compressed. 

 The tail is proved to have been rather long. The scapula exhibits a large 



