308 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



the strata of the horizon of Puerco and the slightly 

 higher ones of Torre j on in New Mexico have fur- 

 nished a rich fauna of placental Mammals, already 

 differentiated into perfectly distinct orders, viz. 

 Ungulates (Condylarthra, Amblypods, Tillodonts), 

 primitive Garni vora (Creodonts) and Primates 

 (Pachylemurians). These faunic elements, excepting 

 the Amblypods and the Tillodonts, are discovered 

 in the unique European deposit of the lowest 

 Eocene (Thane tian stage), that is to say, in the 

 strata of Chalons-sur-Vesle and of Cernay, near 

 Rheims. Finally Ameghino has brought to our 

 notice in Patagonia the very rich fauna of 

 the horizon represented by the Notostylops. Of 

 this fauna a few genera of Condylarthra and 

 Primates show such affinities with the earliest 

 types of the northern hemisphere that we are in- 

 duced to attribute to them an age doubtless differ- 

 ing little from that of the deposits in New Mexico 

 and in the neighbourhood of Rheims. 



It is inadmissible that Mammals so near akin to 

 each other can have appeared independently in 

 three distinct centres, and we can only explain 

 these palseontological affinities by migrations. But 

 of these three regions, the United States, Europe, 

 and Patagonia, which are we to consider the true 

 centre of dispersion of the Placentals ? In other 

 words, which is the country containing the earliest 

 deposit of the remains of these animals ? Until 

 lately no doubt as to this seemed possible. Osborn 

 showed that the stratum of Cernay-les-Rheims was 

 the exact equivalent of the American level of 

 Torrejon, and that there existed in Europe no 



