2 04 CONDYLARTHRA PROTOGONIA chap. 



Creodonta. It has, as in Phenacodus, no orbital ring. The 

 humerus resembles that of a Carnivore rather than that of an 

 Ungulate. The carpus and tarsus are serial. The fibula articu- 

 lates with both the calcaneum and the astragalus, which is not 

 the case with Phenacodus. It is suggested that these animals 

 are ancestral forms of the Chalicotheres. In the brain the 

 hemispheres do not cover the cerebellum. 



More primitive apparently than Phenacodus was the less-known 

 genus Puprotogonia, or Protogonia ^ as it has been called. The best- 

 known species is U. puercensis, so called from its occurrence in the 

 Puerco beds of the American Eocene. It was a slender, long- 

 limbed creatm-e, smaller than Phenacodus, with a long and heavy 

 tail as in that animal. Like Phenacodus it was semiplantigrade, 

 and shows more likenesses to the Creodonta. The skull is only 

 known by a part of the lower jaw with teeth, and by the teeth of the 

 upper jaw. The vertebrae are not entirely preserved, but enough 

 remain to show that the animal had a tail of 1 6 or 1 7 inches, which is 

 a considerable length when compared to its height, about a foot at 

 the rump. In the fore-limb the most noteworthy point is that the 

 ulna has a convex posterior border as in the Creodonts, the same 

 border in Phenacodus being concave. The humerus is slender, with 

 less-marked tuberosities. The fifth digit seems to have been less 

 reduced. The phalanges seem to have liome horny sheaths some- 

 what intermediate between hoofs and claws. The pelvis is 

 described as being, as is also that of Phenacodus, rather like that of 

 the Creodonta. The right hind-limb is known in all its details. 

 It appears that the bones are not serial but interlocking ; this, 

 however, on the views with regard to the relations of these two 

 forms of tarsus mentioned on p. 198, does not militate against 

 regarding Euprotogonia as the ancestor of the genus Phenacodus. 

 The third toe is the pre-eminent one, the animal thus being 

 Perissodactyle. The lateral digits are larger than in Phenaxodus, 

 and the metatarsals and the phalanges are slightly curved, which 

 is again a Creodont character as compared to the perfectly straight 

 corresponding bones of Phenacodus. It seems evident that this 

 animal is to be looked upon as a more ancient type than Phena- 

 codus, even if not as its actual ancestor. 



Another group of the Condylarthra contains the genus 

 Perti'pychiis and some others. Periptychus has the full dentition 



' See W. D. Matthew, Bull. Amer. Miis. Nat. Hist. ix. 1897, p. 303. 



