THE EOCENE OF EUROPE AND NORTH AMERICA 107 



Two orders of archaic hoofed mammals, or ungulates, are known liere, 

 namely: (1) the Amblypoda, or short-footed f(jrms, represented b}' the 

 bunodont Periptychidie, which receive their name from the sculptured 

 sides of the grinding teeth of the type genus Perlptijchus. This family 

 embraces a number of large and small herbivorous mammals, all with a 

 peculiar triangular asymmetry in their superior molar teeth, of consider- 

 able range in size, probably in part ar])oreal in habit. (2) The light-limbed 

 ungulates, or Condylarthra, are doubtfully represented by one genus 

 {Protogonodon) of the family Phenacodontidpe. The gnawing or leaf-eating 

 Hcrbivora of the order Tieniodonta are represented by two families, Sty- 

 hnodontidie and Conoryctidae. This order is also known as Ganodonta 

 (yavos, enamel, oSous, tooth), a name assigned by Wortman when he 

 demonstrated that certain descendants of these mammals present many 

 resemblances to the gravigrade South American edentates, although dis- 

 tinguished by the persistence of dental enamel, which has disappeared in 

 all the true Edentata. Of dou])tful affinity to the Inseetivora are the two 

 genera Miockenus and Oxyacodon. The primitive carnivores, or Creodonta, 

 of this phase have been discovered only in part. They include two families 

 (TriisodontidiE, Oxycla-nidae), represented by five genera. By Wortman 

 the Oxychraidie were regarded as Inseetivora. 



It is noteworthy that not a single representative ancestor of any exist- 

 ing order of mammals is certainly recognized in this assemblage. The 

 possible exceptions are the supposed representatives of the Edentata and 

 Inseetivora, both very ancient orders. The opinion of Cope that the an- 

 cestry of modernized mammals was to be sought in these Puerco forms 

 therefore lacks direct confirmation. The opposite op)inion that the Puerco- 

 Torrejon mammals are not ancestral to the modern mammals was developed 

 by Osborn (1893-1904),* when he applied to them tlie name Meseutheria, 

 indicative of their archaic or Mesozoic character. 



Negatively, therefore, the Puerco is distinguished bj'' the absence of 

 recognizable primates, rodents, carnivores, and of any modern families of 

 insectivores, artiodactyls, and perissodact3ds. A summary of the Puerco 

 mammalian fauna is as follows: 



Genera Species 



Archaic mammals of Triassic ancestry, Marsupialia Dipro- 



todontia 4 5 



Archaic mammals of Cretaceous ancestry 15 24 



Mammals of modern affinity 



Torrejnn Life of the New Mexico and Montana Regions 



Pantolamhda Zone. — All the Mammalia of the Torrejon phase, or Pan- 

 tolambda zone were found about three hundred feet above those of the 



' Osborn, Rise of the Mammalia in North America, 1893; and Ten Years' Progress in 

 Mammalian PaliEontology, 1904. See Bibliography. 



