282 LAND MAMMALS IN THE WESTEKN HEMISPHERE 



and the most ancient fastrapotheres in the narrow sense of the 

 term. The Astraponotus Beds may be either Eocene or 

 OUgocene in date. 



Taking the Casa Mayor faunas as a whole, they were a very 

 numerous and diversified assemblage of small mammals, 

 without a single large one among them. There were no 

 monkeys or rodents; otherwise, the orders were in almost 

 all cases the same as those which made up the Santa Cruz 

 fauna. The marsupials were represented by the opossums 

 and by several of the carnivorous kinds, the only beasts of 

 prey that South America had until the migrations from the 

 north brought in the true Carnivora, late in the Miocene or 

 very early in the Pliocene. There were also numerous small 

 marsupials of peculiar type, of which the last living survivor 

 is Ccenolestes, of Ecuador. Throughout the stage, armadillos 

 were present in considerable variety, but are known only 

 from the bony plates of the carapace, and therefore httle can 

 be determined as to their relationships to the modern families. 

 Only a single and very .problematical genus of the fground- 

 sloths, which afterwards throve so mightily in the Miocene 

 and Pliocene, has been obtained and that in the later portion 

 of the stage. 



The orders of hoofed mammals were represented by many 

 small animals, most of which are known only from the teeth, 

 which show these Casa Mayor genera to have been far more 

 primitive and less specialized than their descendants in the 

 Deseado and Santa Cruz stages. All of them had the low- 

 crowned grinding teeth of the browsers, and no grazers were 

 then in existence, so far as is known. No ftoxodonts, in the 

 more restricted sense of that term, have been found, but the 

 two allied suborders of the fTypotheria and fEntelonychia 

 were numerously represented. Of the former there were two 

 families and of the latter three, which is more than in the 

 Deseado or Santa Cruz formations. One of the families of 

 the fEntelonychia (fNotostylopidae) consisted of very small, 



