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SCIENCE 



[N. S. Vol. XLIII. No. 1100 



been found and must have arrived in South 

 A m erica at a relatively early date, for sev- 

 eral highly peculiar and aberrant types 

 were developed. One of these {Hyper- 

 hippidium) found in the Andes, was a 

 small, mountain horse, with remarkably 

 short feet which were well adapted to 

 climbing. Tapirs ranged down into Argen- 

 tina, much farther south than at present, 

 but were not otherwise noteworthy. The 

 range of the llamas also was much greater 

 than it is to-day; now, they are restricted 

 to the colder parts of the continent, but in 

 the Pleistocene they extended into the for- 

 ests of Brazil. Two antelopes have been 

 reported, a family of which Notogtea has 

 now no representatives. Mastodons of 

 several species have been found in many 

 parts of the continent, but, curiously 

 enough, the true elephants did not accom- 

 pany them in their southward migration. 

 Why this was, it is difficult to say; per- 

 haps because the North American ele- 

 f)hants, which came in by way of Siberia, 

 were cold-country species and therefore 

 unable to cross the tropics. 



The Pleistocene extinctions worked even 

 greater havoc among the autochthonous 

 forms than among the immigrants, destroy- 

 ing almost all of the very large mammals 

 whose history and development may be 

 traced back, step by step, through the suc- 

 cessive divisions of the South American 

 Tertiary. The visitor to the museums of 

 La Plata and Buenos Aires can not but be 

 deeply impressed by the number and va- 

 riety of the ground-sloths and glyptodonts 

 from the Pampean formation which are 

 there displayed; it is immediately evident 

 that the members of those groups which 

 inhabited Pleistocene North America were 

 but the outlying stragglers of the far more 

 numerous and incomparably more diversi- 

 fied assemblage found in South America. 

 They were indeed a strange and grotesque 



host of ponderous, slow-moving, but inof- 

 fensive plant-feeders, which, together with 

 the almost equally bizarre indigenous 

 hoofed animals, gave a most outlandish 

 character to the fauna. The ground-sloths 

 ranged in size from a tapir to a short-legged 

 elephant; Megatlierium even surpassing 

 the elephants in massiveness of trunk and 

 limbs. The glyptodonts differed much 

 among themselves in size, in the character 

 of the head, in the form of the solid and 

 heavy carapace, but especially in the arma- 

 ture of the tail, which, in some cases at 

 least, must have been a formidable weapon 

 of defence. It is usual to call the glypto- 

 donts "giant armadillos," but that term is 

 more properly applied to certain huge ani- 

 mals, as large as a rhinoceros, which were 

 true armadillos. The largest existing spe- 

 cies of the group is hardly more than a 

 yard long. 



Among the hoofed animals, three of the 

 native groups, the toxodonts, typotheres 

 and litopterns, which were so remarkably 

 abundant and varied in the Santa Cruz 

 Miocene, persisted into the Pleistocene and 

 then became extinct. Evidently they had 

 begun to decline long before that epoch, 

 possibly because of the competition of the 

 more advanced and highly organized in- 

 truders from the north, though certain series 

 continued to progress in size and differen- 

 tiation of structure until the end of their 

 career. One of the most characteristic of 

 these animals was Toxodon, of which two 

 skeletons are mounted in the La Plata Mu- 

 seum. The genus was found by Charles 

 Darwin, who says of it: "Perhaps one of 

 the strangest animals ever discovered; in 

 size it equalled an elephant or megathe- 

 rium, but the structure of its teeth, as Mr. 

 Owen states, proves indisputably that it 

 was intimately related to the Gnawers 

 [i. e., Eodentia] ... in many details it is 

 allied to the Pachydermata : judging from 



