SUCCESSIVE MAMMALIAN FAUNAS 245 



the Australian phalangers. At the present day South America 

 contains no Insectivora, but in the Santa Cruz there was one 

 family (fNecrolestidae) of this order which bore considerable 

 resemblance to the "golden moles" of South Africa. An 

 extraordinary variety of rodents inhabited Patagonia in Santa 

 Cruz times, all of them belonging to the Hystricomorpha, or 

 porcupine suborder, and all referable to existing South Ameri- 

 can families. There were none of the northern forms of ro- 

 dents, neither rats, mice, squirrels, marmots, hares, nor 

 rabbits, but a very numerous assembly of tree-porcupines, 

 cavies, chinchillas, coypus and the like. The genera, though 

 closely allied to existing ones, are all extinct, and the animals 

 were very generally smaller than their modern descendants. 

 A few small monkeys of unmistakably Neotropical type have 

 been found, but like other arboreal and forest-living animals, 

 they are very rare among the fossils. 



The Edentata were more abundant and diversified than at 

 any other time in South American history of which the record 

 is preserved. Two of the modern subdivisions of this order 

 have not been certainly identified in the Santa Cruz collections, 

 the arboreal sloths and the anteaters, and though they may be 

 found there at any time, it will only be as stragglers from the 

 warmer forested regions to the north, where these forms had 

 doubtless long been present. Unfortunately, however, nothing 

 is directly known concerning the life of those regions in Miocene 

 times. On the other hand, three groups of edentates, two of 

 them now extinct, were very copiously represented in the Santa 

 Cruz formation, the armadillos, fglyptodonts and fground 

 sloths. Of the many armadillos, some quite large, others 

 very small, only a few can be regarded as directly ancestral 

 to those now in existence ; the truly ancestral forms were 

 probably then living in the forests of Brazil and northern 

 Argentina, in the same areas as the ancestral tree-sloths and 

 anteaters. In comparison with the giants of the Pliocene 

 and Pleistocene, the Santa Cruz fglyptodonts were all small, 



