THE EOCENE OF EUROPE AND NORTH AMERICA 103 



This Basal Eocene stage is further distinguished by the presence of 

 numerous chprotodont marsupial multituberculates of the family Plagiaula- 

 cidie, and by many other very primitive mammals. 



It is also distinguished by the al)sence of any mammals belonging to 

 modernized faniili(^s. These first make their appearance on both con- 

 tinents in the Lower Eocene (Wasatch) in what is known as the Coryphodon 

 Zone, probabl}' equivalent to the Upper Landenian of Belgium or the 

 Sparnacian of France. 



The chief distinction of this mammal fauna is that it represents a 

 survival of the mammalian life of the Age of Reptiles, and so far as we 

 know it now this life is all of the archaic type. We are, in fact, witnessing 

 the close of a faunal phase which opened well back in Cretaceous times. 



Basal Eocene of Europe 



Thanetian Formation. — The Basal Eocene of Europe is known as the 

 Thanetian Stage; it is named after the Isle, or promontory, of Thanet, at 

 the mouth of the Thames. As above described on p. 99, it is divided into 

 inferior and superior levels. In France it is typified by the fluvio-marine glau- 

 conie de la Fere, from which the single famous bear-like creodont Arctocyon 

 primcevus was described in 1841. With the superior level (Upper Thane- 

 tian) is paralleled the fiuvio-marine gravel deposit of Cernay, near Rheims, 

 from which the famous "fauna of Cernay" was described by Lemoine.^ 



Characteristic This very rich Cernaysian or Upper Thanetian 



Mammals fauna is nearly of the same age as the Torrejon fauna 



Plagiaulacids of northern New Mexico; that is, its age is a little 



Adapisoricids more recent than the underlying true Puerco fauna of 



Lemuroids (?) New Mexico. It contains small insectivores, lemur- 



Insectivores, (?) like mammals, a few hoofed mammals, and many car- 

 or Condylarths (?) nivores. It is especially interesting to compare the 

 Arctocyonids teeth of Neoplagiaulax (Cernaysian) with those of 



Oxyclaenids Ptilodus (Torrejon) as in a similar stage of evolution; 



Triisodonts these are small, gnawing, diprotodont marsupials, 



which may be descended from Plagiaidax of the 

 Upper Jurassic, The Insectivora are represented by members of the 

 family Adapisoricida, somewhat analogous to the tree shrews (Tupaia). 

 Primitive monkeys, possibly lemuroids, are represented by small animals 

 referred to the Plesiadapidse. More doubtful is the identification of the 

 teeth of the herbivorous tuberculate pattern with that of one of the 

 primitive cursorial ungulates (Euprotogonia) of the hoofed order Con- 

 dylarthra of the Torrejon. Pleuraspidotherium somewhat resembles 

 Meniscotherium, the primitive ungulate or condylarth of more recent 



' See Lemoine, various papers listed in Bibliography. 



