The geographical distribution of animals, with a study of the relations ...
The geographical distribution of animals, with a study of the relations ... The geographical distribution of animals, with a study of the relations ...
142 DISTRIBUTION OF EXTINCT ANIMALS. [part 11.the American Pliocene and Miocene periods, abounding ingenera and species ; whereas in Europe the group only exists inthe Post-Pliocene or Lower Pliocene, with one Upper Miocenespecies of Camelus in N. India. The Anthracotheridae (extinct),found only in the Upper Miocene of France and India, reacheven the Lower Eocene in America.These facts may be due, in part, to a want of strictco-ordinationbetween the Tertiary deposits of Europe and North America,—in part to the imperfection of the record in the latter country.Yet it does not seem probable that they are altogether due tothese causes, because the Miocene beds, which are by far thebest know T n in America as in Europe, exhibit deficiencies of thesame kind as the less known Eocene deposits. The fossil faunaof both countries is so rich, that we can hardly impute great andwell marked differences to imperfect knowledge; yet we findsuch important families as the Civets, Hyamas, Giraffes, andHippopotami absent from America, with the Weasels, and Antelopesalmost so ; while America possesses almost all the Camelidaa,two peculiar orders, Dinocerata and Tillodontia, and four remarkablypeculiar families, Limnotheridse, Lemuravidse, Oreodontidseand Brontotheridae. If then the facts at present known representapproximately the real time-relations of the groups in questionon the two continents, they render it probable that weasels, bears,true horses, swine, oxen, sheep and antelopes, originated on theOld World continent, and were transmitted to America duringsome part of the Miocene period ;while camels originated in theNew World, and somewhere about the same time passed over toEurope. Of the extinct families common to the two hemispheres,the Anthracotheridse alone seem to have had anAmerican origin. Of the genera common to the two countries,almost all seem to have had a European origin, the only generaof equal date being the two rhinoceroses and three Anchitheridse;but if the Brontotheridse are allied to the Ehinocerotidae,these latter may have originated in America, althoughnow anexclusively Old World type. These conclusions are not improbablewhen we consider the much greater size of the OldWorld continents, extending far into the tropics and probably
chap, vii.] MAMMALIA OF THE NEW WORLD. 143always more or less united to the tropical areas ; while theevidence of the extinct mammalia themselves shows, that SouthAmerica has been for the most part isolated from the northerncontinent, and did not take part in the development of itscharacteristic Tertiary fauna.Before speculating further on this subject, it will be well tolay before our readers a summary of South American palaeontology,after which we shall be in a better position to drawcorrect inferences from the whole body of the evidence.South America.Unfortunately, our knowledge of the interesting fossil faunaof this continent, is almost wholly confined to the Post-Plioceneand Pliocene periods. A few remains have been discovered indeposits believed to be of Eocene age, but nothing whateverrepresenting the vast intervening period, so rich in peculiarforms of animal life both in North America and Europe.Fauna of the Brazilian caves.—What we know of the Post-Pliocene period is chiefly due to the long-continued researchesof Dr. Lund in the caves of Central Brazil, mostly situated ina district near the head waters of the San Francisco riverin the Province of Minas Geraes. The caves are formed inlimestone rocks, and are so numerous that Dr. Lund visitedthousands, but only sixty contained bones in any quantity.These caves have a floor of reddish earth, often crowded withbones. In one experiment, half a cubic foot of this earthcontained jaws of 400 opossums, 2,000 mice, besides remainsof bats, porcupines and small birds. In another trial, thewhole of the earth in a cavern was carried out for examination,amounting to 6,552 firkins ; and, from a calculationmade by measured samples, it was estimated to containnearly seven millions of jaw-bones of cavies, opossums, porcupines,and mice, besides small birds, lizards, and frogs. _ Thisimmense accumulation is believed to have been formed fromthe bodies of animals brought into the cavern by owls ;and,as these are unsocial birds, the quantity found implies an
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chap, vii.] MAMMALIA OF THE NEW WORLD. 143always more or less united to <strong>the</strong> tropical areas ; while <strong>the</strong>evidence <strong>of</strong> <strong>the</strong> extinct mammalia <strong>the</strong>mselves shows, that SouthAmerica has been for <strong>the</strong> most part isolated from <strong>the</strong> nor<strong>the</strong>rncontinent, and did not take part in <strong>the</strong> development <strong>of</strong> itscharacteristic Tertiary fauna.Before speculating fur<strong>the</strong>r on this subject, it will be well tolay before our readers a summary <strong>of</strong> South American palaeontology,after which we shall be in a better position to drawcorrect inferences from <strong>the</strong> whole body <strong>of</strong> <strong>the</strong> evidence.South America.Unfortunately, our knowledge <strong>of</strong> <strong>the</strong> interesting fossil fauna<strong>of</strong> this continent, is almost wholly confined to <strong>the</strong> Post-Plioceneand Pliocene periods. A few remains have been discovered indeposits believed to be <strong>of</strong> Eocene age, but nothing whateverrepresenting <strong>the</strong> vast intervening period, so rich in peculiarforms <strong>of</strong> animal life both in North America and Europe.Fauna <strong>of</strong> <strong>the</strong> Brazilian caves.—What we know <strong>of</strong> <strong>the</strong> Post-Pliocene period is chiefly due to <strong>the</strong> long-continued researches<strong>of</strong> Dr. Lund in <strong>the</strong> caves <strong>of</strong> Central Brazil, mostly situated ina district near <strong>the</strong> head waters <strong>of</strong> <strong>the</strong> San Francisco riverin <strong>the</strong> Province <strong>of</strong> Minas Geraes. <strong>The</strong> caves are formed inlimestone rocks, and are so numerous that Dr. Lund visitedthousands, but only sixty contained bones in any quantity.<strong>The</strong>se caves have a floor <strong>of</strong> reddish earth, <strong>of</strong>ten crowded <strong>with</strong>bones. In one experiment, half a cubic foot <strong>of</strong> this earthcontained jaws <strong>of</strong> 400 opossums, 2,000 mice, besides remains<strong>of</strong> bats, porcupines and small birds. In ano<strong>the</strong>r trial, <strong>the</strong>whole <strong>of</strong> <strong>the</strong> earth in a cavern was carried out for examination,amounting to 6,552 firkins ; and, from a calculationmade by measured samples, it was estimated to containnearly seven millions <strong>of</strong> jaw-bones <strong>of</strong> cavies, opossums, porcupines,and mice, besides small birds, lizards, and frogs. _ Thisimmense accumulation is believed to have been formed from<strong>the</strong> bodies <strong>of</strong> <strong>animals</strong> brought into <strong>the</strong> cavern by owls ;and,as <strong>the</strong>se are unsocial birds, <strong>the</strong> quantity found implies an