KNOWLEDGE. 



[January 1, 1894. 



takes its English name from the spur on its wings and its 

 loud cry — the latter being sometimes heard when the bird 

 is so high in the air as to be almost or quite invisible. 

 Among characteristic South American reptiles may be 

 mentioned iguanas (a name often applied incorrectly to 

 lizards from other parts of the world) and caimans; the 

 latter being a group of alligators, distinguished by having 

 an armour of bony plates on the under as well as on the 

 upper surface of the body. The huge horned frogs {Cera- 

 toplinjs) are likewise distinctive of the country among the 

 batrachians. 



Such are a few of the leading features of the existing 

 fauna of South America, which are sufficient to show how 

 totally different is the animal life of this country from 

 that of all the rest of the world. If, however, we go back 

 to the late geological periods of the earth's history, we 

 shall find that this peculiarity and disthictness of the 

 South American fauna was even more inteusitied than it 

 is at the present day ; this being largely due to the 

 circumstance that at one time the Isthmus of Darien did 

 not exist — so that the northern and southern portions of 

 the New World were disconnected. Since the time when 

 a connection was formed between the two continents, their 

 faunas have, however, naturally tended to blend together, 

 and hence at the present day, and during the Pleistocene 

 period, the animals of South America are less sharply 

 differentiated from those of the northern half of the 

 continent than would have been the case had the Isthmus 

 of Darien not been formed. It is further interesting to 

 note that during the Tertiary period there appears to have 

 been some kind of connection between the faunas of South 

 America and Australia. 



The country that has afforded us the most information 

 with retrard to the extinct fauna of South America is the 

 Argentine Republic, which includes not only Buenos Ayres 

 and the adjacent provhices forming Argentina proper, but 

 likewise the whole of Patagonia. Confining our attention, in 

 the first place, to the province of Buenos Ayres and some of 

 the neighbouring districts, we may note that the greater 

 part of this vast tract of country is one boundless level plain 

 formed by an alluvial deposit of rich black mud Inought 

 down from the higher lands of the interior by the tribu- 

 taries of the Eio de la Plata, and which constitutes the 

 most extensive pasture-land in the world. Near Buenos 

 Ayres and the valley of the Eio de la Plata this alluvial 

 deposit, which in places alternates with sandy beds, is of 

 immense thickness ; * but further to the south it thins out 

 rapidly. In some places in the neighbourhood of La 

 Colina, about a hundred miles from Bahia Blanca, for 

 instance, the black soil is not more than a couple of feet 

 in thickness, and is underlain by a hard white calcareous 

 deposit, locally known as " tosca," and much resembling 

 some of the deposits formed by hot springs.! That the 

 black alluvial deposit, which, from forming the whole of 

 the pampas, or plain country, is known to geologists as the 

 Pampean formation, is of fresh-water origin, is perfectly 

 clear ; and it is probable that it has been largely formed 

 in marshes and swamps, one of its most striking features 

 being the total absence of pebbles or stones. Indeed, 

 throughout the country, except in the neighbourhood of 

 the mountains, there is not a vestige of rock or stone to 

 be seen, unless it be in the few places where the aforesaid 

 " tosca " has been brought to the surface. In spite of its 

 fresh- water origin, there is, however, evidence that portions 

 of the Pampean formation have been submerged beneath 



* Near Buenos Ayi'es it has been bored into for depths of fifty and 

 ninety feet. 



t At Buenos Ayres tlie alluvial deposit itself is ealled '' tosea." 



the sea. For instance, in the neighbourhood of the city of 

 La Plata there occurs a bed of marine shells overlying the 

 alluvial mud ; all the species of molluscs being now found 

 living in the Bay of Jlonte Video. I have also observed a 

 similar bed at Santa Lucia, in the Banda Oriental, at an 

 elevation of about one hundred feet above the sea, which 

 was overlain by a considerable thickness of sands, and the 

 same deposit occurs far inland at the town of Parana. 

 From these data it may be inferred that after the temporary 

 subsidence of the pampas, during which the marine beds 

 were deposited, there has been a considerable elevation 

 (which is probably still going on) of the whole country ; 

 and that the whole of these movements have taken place 

 at a very recent epoch indeed. 



At tlie present day the Argentine pampas, with the 

 exception of a few willows along the river courses, is 

 practically destitute of trees (save where they have of late 

 years been planted around the various settlements), and 

 forms a boundless sea of grass, relieved here and there by 

 tussocks of the tall pampas grass, or giant thistles, and 

 adorned in spring with the scarlet verbena and other bright- 

 hued flowers. Till the introduction of the countless herds 

 of horses, cattle, and sheep, which now roam over its 

 extent, this vast tract of country was tenanted by the 

 guauaco, the pampas deer, the viscacha, and the rhea, 

 which, with the exception of certain carnivores, were 

 almost the only animals of any size to be found throughout 

 its length and breadth. 



The rich black alluvial mud of the pampas, which, as we 

 have seen, is entirely of fresh-water origin is, however, 

 the tomb of thousands, if not millions, of the skeletons and 

 bones of a host of extinct animals, which tell us that the 

 country was once inhabited by a fauna stranger than that 

 found in any other jsart of the world at any epoch of its 

 history. While many of these extinct creatures were 

 allied to the existing South American mammals, although 

 of vastly greater bodily size, others, of equally gigantic 

 dimensions, W'ere utterly unhke all known animals, either 

 living or extinct. As we intend to describe some of these 

 extinct mammals in succeeding articles, we shall make but 

 brief mention of them here. We may observe, however, 

 that while the gigantic glyptodons were the representatives 

 of the diminutive armadillos of to-day (although some of 

 the latter flourished side by side with their huge cousins), 

 the megathere, which rivalled an elephant in bulk, together 

 with its allies the mylodons, were akin both to the sloths 

 and the anteaters of Brazil, and as they were evidently 

 terrestrial in habits they may be conveniently spoken of as 

 ground sloths. From the structure of these latter animals, 

 which were pretty evidently adapted to sit up on their 

 massive haunches and tear down the branches of trees 

 with their powerful front claws, we may infer that the 

 physical features of this part of Argentina must have been 

 very different from what they are at present, and that in 

 place of continuous tracts of unbroken grassy plain there 

 must have been large areas of forest land, as in Brazil 

 at the present day. In these forest tracts may have 

 wandered the two species of mastodons which were the 

 contemporaries of the gror.nd sloths ; but the existence at 

 the same time of several species of horses (some closely 

 akin to living species, while others were markedly distinct) 

 seems to point to the presence of grassy plains alternating 

 with the forest tracts. The same is probably indicated by 

 the numerous species allied to the guanaco, which 

 flourished at the same time, and some of which attained 

 the dimensions of a camel ; while the various kinds of deer 

 may also have inhabited the same regions. The gigantic 

 hoofed mammal, known as the To.rodon, which had ever- 

 growing teeth'c ; t hose of a rodent, was. however, prob- 



