Marsh Collection, Pectbody Museum. 431 



the Tertiary deposits of Europe. The succession of these 

 strata is not so complete in Europe as in America, and their 

 record of the appearance and disappearance of mammalian 

 forms is less perfect ; however, it is sufficiently complete to 

 give the broad features of mammalian succession. While the 

 Jurassic mammals are well represented, and correspond closely 

 genus for genus with those from the Wyoming beds in America, 

 the Cretaceous forms as well as those corresponding to our 

 Puerco have not been found in Europe. The oldest Tertiary 

 beds in Europe from which mammalian remains have been 

 obtained are those at Cernay in France. According to Osborn,* 

 this fauna bears a close resemblance and corresponds to 

 that of our Torre jon. It is in the succeeding Wasatch or its 

 near equivalents, however, that the most striking similarity 

 occurs. Exposures of beds of this age are found at many 

 localities in Europe, and a fauna almost equal in richness and 

 variety to that of America is known. Just as in America, the 

 sudden introduction of the same entire orders — the true Pri- 

 mates, the Rodentia, Artiodactyla, Perissodactyla, Insectivora, 

 as well as many suborders, families, and genera of the various 

 other groups — takes place without previous warning. The 

 most remarkable fact is the similarity observable in the two 

 faunse. In many instances, the species belong to the same 

 genera which are common to the two Hemispheres. f In the 

 following succession, the introduction of new types of the same 

 general character as those in America proceeds in the same 

 sudden and unheralded manner. 



]S"ow, what is the significance of these facts and from what 

 source or sources were these faunae derived ? In the case of the 

 Puerco, we have the sudden introduction of thirty or more 

 species belonging mostly to a group of mammals hitherto 

 entirely unknown upon the earth. The species of the Mesozoic 

 types may be accounted for by derivation from the preexisting 

 mammals whose remains are found in the underlying Creta- 

 ceous, but as regards the Entherian element of the fauna, no ear- 

 lier traces of it have ever been found, and he who would main- 

 tain that this new Entherian element in the Puerco fauna 

 developed from any of the known Cretaceous forms, in the 

 ordinary course of evolution, would be so utterly Jacking in a 

 proper sense of morphological proportion as to be a very 

 unsafe guide in such matters. The Laramie or Upper Creta- 



*A Review of the Cernaysian Mammalia, Proc. Phila. Acad., 1890. 



f The more important of the nearly related or identical genera common to 

 Europe and America in the Wasatch or its near equivalent in Europe, thus 

 far identified, are Coryphodon, Phenacodus, Hyracotherium , Pantolestes ?, 

 Paramys and Plesiarctomys, Heptodon and Lophiodoii, Arctocyon and Anac- 

 odon, Pcdceonictis, Sinopa and Pr&oiverra, Oxycena, Calamodon, Hyopsodus, 

 and others. 



