SUCCESSIVE MAMMALIAN FAUNAS 277 



For the most part, the families were the same as those of the 

 Bridger fcreodonts, but the genera all were different. The 

 toxysenids {^Oxycena) were much smaller and lighter than the 

 large and massive representatives found in the middle Eocene, 

 and their teeth were not so cat-like. Another group of pre- 

 daceous animals {^Palceonictis) which also inhabited Europe, 

 but did not survive the lower Eocene in either continent, 

 had short, broad and very cat-like heads. The fmesonychids 

 were far larger than those of the Bridger, a departure from the 

 ordinary rule, and the several species of the common Wasatch 

 genus {'fPachycena) had grotesquely large heads. A family 

 (fArctocyonidae), of very extensive geographical range and 

 great antiquity, had its last representatives here in a very 

 curious animal CfAnacodon) which had the flat-crowned, 

 tuberculated grinding teeth of the bears and the enlarged, 

 scimitar-like upper canines of the fsabre-tooth cats. Such a 

 combination seems utterly incongruous and no one would 

 have ventured to predict it. The progressive family of jcre- 

 odonts (fMiacidse) was already quite numerously repre- 

 sented, but only by small forms, which must have preyed 

 upon small mammals, birds and lizards. 



Two archaic orders of hoofed mammals were fairly numer- 

 ous. One, the fCondylarthra, comprised quite small, five- 

 toed animals, with long tails and short feet and extremely 

 primitive in structure. A genus {^Phenacodus) of this order 

 was long regarded as being ancestral to most of the higher 

 orders of ungulates, but this belief has proved to be untenable. 

 More numerous were the fAmblypoda, one genus of which 

 i'fCoryphodon), though persisting into the Wind River, was 

 especially characteristic of the Wasatch. The fcoryphodonts 

 were the largest of lower Eocene mammals, and some of the 

 species equalled a tapir or small rhinoceros in length and height, 

 but had heavier limbs ; as the skeleton conclusively shows, 

 these must have been heavy, clumsy and exceptionally ugly 

 brutes, with formidable tusks, large head, but relatively more 



