Imágenes de páginas
PDF

Fig. 11). They are entirely confined to the higher ranges of the Andes and to the desolate plains of Patagonia.

The Deer (Cervidm) of the Neotropical Region all belong to two peculiar genera (Cariacus and Pudua), of which the former extends northwards throughout the United States

[graphic]

Fig. 11.—The Lama. (Lama peruana.)

to British Columbia, while the latter is found only in Western South America.

Finally, the Tapirs (Tapiridm) are represented by four species, all of which are peculiar to this region, the only other existing Tapir known being the Indian Tapir of the Malay Peninsula. The explanation of this curious case of discontinuous distribution is afforded by the past history of the group. During Miocene and Pliocene times, members of this genus and its allied forms were found both in North America and also throughout the Old World from France to China. This gives us direct evidence of the former much wider extension of the family of Tapirs, and bridges over the present great gap in its distribution.

As already stated, the fauna of the Neotropical Region is almost as remarkable for the absence of certain families as it is for the presence of peculiar forms. This is specially noticeable in the Ungulates. There is no existing representative of the four great families of the Oxen, Rhinoceroses, Horses, and Elephants in this region, though remains of the latter two groups have been found in most recent deposits of Argentina. Here they were probably immigrants from the north, which survived but a short time in this locality.

Turning now to the Rodents, we find that out of the four chief divisions into which this order is separated—the Squirrels (Sciuromorpha), the Mice (Myomorpha), the Porcupines (Hystricomorpha), and the Hares (Duplicidentata)—the first two and the last contain very few peculiar genera and no peculiar families in this Region. But, on the other hand, out of the six families of Hystricomorpha four are restricted to this region, while of the remaining two, one (the Octodontidm) is found elsewhere only in Africa, and the other, the Porcupines (Hystricidm) is of wide distribution. Moreover, all the Neotropical genera of the Hystricomorphine division are, without exception, confined to this region.

The Carnivores, which follow next, are well represented in the Neotropical Region, but belong generally to families of wide distribution. But one family, the Raccoons (Procyonidm), with the exception of a single genus (JOlurus), which is perhaps doubtfully referred to it, is entirely confined to the New World. On the other hand, the Viverridm, so widely spread in the Old World, are entirely absent in America.

With the exception of some four or five species of Shrews, which have obviously spread southwards from the Nearctic Region, wherein they are found in considerable numbers, the Insectivores are represented in the Neotropical Region only by a single remarkable family. This is the Solenodont—a characteristic form of the Greater Antilles —absolutely unknown elsewhere. The Insectivores are usually considered to be the most generalised of all the mammalian orders, and to be the least changed descendants of the ancestral group from which most of the other orders of mammals have originated. If this be the case, it seems strange that we should find no traces of them on the continent of South America, which was, doubtless, long isolated from the rest of the world, and which still contains many representatives of primitive and declining types. The palseontological history of the Insectivores is, however, as yet very incomplete, as very few fossil forms of this order have been described. It is, therefore, possible that when future discoveries have increased our knowledge on this subject, this seeming anomaly may be explained.

The Neotropical Bats (Chiroptera) are of much interest; they are included in three families, of which two (Vespertilionidm and Emballonuridx), although containing several peculiar genera, are found in other parts of the world, but the third (Phyllostomatidm) is entirely confined to this region.1

This family, which numbers among its members the true Vampires or blood - sucking bats (Desmodus and Diphylla), is a very considerable one, numbering at least sixty species, distributed among thirty-three genera, which are doubtless still to be supplemented by future discoveries.

Finally, the Neotropical Region possesses two families of Monkeys, the Marmosets (Hapalidm) and the Capuchins (Cebidw), neither of which is found elsewhere. Moreover, both these groups are distinguished from their Old World allies by very important anatomical characters, which render them absolutely distinct from the Old World monkeys and apes.

As a representative of this latter family we give a figure of the Barrigudo Monkey (Lagothrix humboldti) of Upper Amazonia (Fig. 12, p. 64) of which Mr. Bates has written us an excellent account in his well - known "Naturalist on the Amazons."

Summarising these statements, we find that the Neotropical Region is characterised by the exclusive possession of no less than ten families of mammals, namely:—

Bradypodidse (Sloths); Caviidae (Guinea-pigs);

Myrmecophagidse (Ant-eaters); Solenodontidse (Solenodonts);

Chinchillidse (Chinchillas); Phyllostomatidse (Vampire bats);

Dasyproctidse (Agoutis); Hapalidse (Marmosets);

Dinomyidse (Dinomys); Cebidse (Capuchin monkeys);

and by the presence of about 130 genera, of which about 103 are restricted to its boundaries.

On the other hand, when we compare the fauna of the

1 One species, Macrotut californicus, has wandered as far north as California.

Neotropical with that of other regions, the deficiencies or "lipotypes" are manifestly considerable. For example, the following ten families of mammals, all fairly well

[graphic][ocr errors]

spread over the rest of the world except Australia, are entirely absent from this region:—

Bovidse (Oxen).
Equidse (Horses).
Elephantidse (Elephants).
Lagomyidse (Pikas).
Viverrid» (Civets).
Talpidas (Moles).

Pteropidse (Fruit-bats).
Lemuridse (Lemurs).
Cercopithecidse (Old World

monkeys).
Simiidse (Anthropoid apes).

« AnteriorContinuar »