XII 



LIFE OF TERTIARY PERIOD 235 



Another sub - order, Astrapotheria, were more massive 

 animals, some of which equalled the rhinoceros in size. They 

 consist of two distinct genera, only found in the Patagonian 

 deposits of Mid-Tertiary age. 1 



Still more remarkable is another group — the Toxodontia 

 — sometimes exceeding the rhinoceros in bulk, but with 

 teeth which approached those of the Rodentia ; of these there 

 are various forms, which are grouped in three distinct families. 

 The skeleton of one of the largest species of this sub-order is 

 shown in Fig. Sy. Yet another distinct sub-order, Pyrotheria, 

 which in its teeth somewhat resembled the extinct European 

 Dinotherium, and which had a large pair of tusks in the 

 lower jaw, is found in the earlier Tertiary strata of Santa Cruz 

 in Patagonia. The elephants also had a representative 

 among these strange monsters in the form of a species of 

 Mastodon, a genus also found in North America. 



The very numerous and peculiar South American rodents 

 commonly called cavies, including the familiar guinea-pig, 

 are well represented among these fossils, and there are many 

 extinct forms. Most of these are of moderate size, but one, 

 Megamys, said to be allied to the viscachas, is far larger 

 that any living rodent, about equalling an ox in size. 



Perhaps more remarkable than any of the preceding are 

 the extinct Edentata which abound in all these deposits. 

 The entire order is peculiar to America, with the exception 

 of the scaly ant-eater of Asia and the aard-vark of South 

 Africa, and there is some doubt whether these last really 

 belong to the same order. The living American edentates 

 comprise three families, generally known as sloths, ant-eaters, 

 and armadillos, each forming a well-marked group and all 

 with a fair number of distinct species. But besides these, 

 two extinct families are known, the Glyptodontidae and the 

 Megatheriidae, the former being giant armadillos, the latter 

 equally gigantic terrestrial sloths. Both of these lived from 

 the Miocene period almost to our own time, and they are 

 especially abundant in Pliocene and Pleistocene deposits. 

 Some of the extinct forms of armadillo were very much 

 larger than any now living ; but it is among the Glyptodonts, 

 which had a continuous shield over the whole body, that the 



A Geographical History of Mammals, R. Lydekker, F.R.S., etc., 1896, p. 81. 



