Imágenes de páginas

the Virgin Islands on the west, and the Anguilla group on the east.

On the whole the Lesser Antilles appear to have derived their fauna direct from South America, but probably in times considerably remote, and without the assistance of a land-connection. The almost complete absence of terrestrial mammals and of representatives of sedentary and non-migratory birds in the Lesser Antilles seems to show this. For instance, Grenada possesses only fifteen land-birds also found in Trinidad, and of these none belong to the sedentary families, although the two islands are only separated by an interval of seventy-five miles of sea. On the whole, therefore, it seems probable that, although the Lesser Antilles have derived the bulk of their fauna from South America, they have never been directly connected with that continent.

Of the Greater Antilles, Jamaica and Cuba have by far the richest endemic faunas, whereas in Hayti and Porto Rico the total number, as well as the number of endemic species, is considerably smaller. Jamaica, therefore, with its small area (one-tenth of that of Cuba, one-eighth of that of Hayti, and a little more than that of Porto Rico), and in spite of its more isolated position, contains on the whole, so far as our present knowledge goes, the richest fauna.

This may, perhaps, be explained by the fact that between the north-east corner of Honduras and Jamaica there stretches a series of more or less shallow banks, so that a comparatively slight elevation of the intervening seabottom would very nearly connect Jamaica with the mainland.

Whether such a complete land-connection (or only an

[ocr errors]

approximation of land areas) by this route ever existed, cannot at present be definitely settled. On the one hand, as pointed out by Mr. Chapman, the disproportionately rich fauna of Jamaica, the shallow sea, and the West Indian affinities of Swan Island (as shown by the presence of a species of Capromys) lead to such a direct connection. On the other hand, the scarcity of land-mammals in Jamaica and Cuba, and the absence of many families of Birds found on the mainland, rather point the other way. The help in these questions to be derived from palæontology is up to this time very scanty. Almost the only remains of fossil mammals that have been yet obtained from the West Indies are certain detached teeth and some fragmentary bones, found in some caves in the island of Anguilla, which is situated just to the east of the deep channel separating the Greater from the Lesser Antilles, and must, therefore, be included in the latter province. These remains have been described by Professor Cope (5), who considers then to be related to the Chinchillas, a family of rodents confined to South America.

The nature of the Mammalian genera of the Antillean Region is summarised in the subjoined table :

[blocks in formation]


This Sub-region, as has been already shown, contains the coast-lands of Mexico lying along the Pacific and Atlantic shores from Mazatlan on the north on one side, and from the Rio Grande on the other, together with the whole of Central America from the Isthmus of Tehuantepec to that of Panama.

As regards the fauna of this part of America, we are fortunate in being able to refer to the excellent account of it contained in the“ Biologia Centrali-Americana” of Messrs. Salvin and Godman. The volume relating to the mammals in this work was undertaken by Mr. Alston, and finally completed after his death by one of the authors of this work in 1882 (3). Out of a total of sixty-nine genera of mammals represented in this Sub-region, only two seem to be absolutely restricted to it, and these, moreover, are genera of bats, which may possibly be found at some future time to extend into the main South American continent.

Of the sixty-seven non - peculiar Central - American genera of mammals, forty-one are Neotropical typesthat is, found also in one or more of the other Sub-regions of this Region-five are Nearctic, nine are found both in the Nearctic and in other Sub-regions of the Neotropical Region, and twelve are cosmopolitan, or, at any rate, found in some part of the Old World as well as in the New.

These facts show conclusively the thoroughly Neotropical character of the Central-American Sub-region, which, although the admixture of northern forms has really made very little progress, may be defined as that part of the Neotropical Region which has been subjected to an incursion of Nearctic types.

The Marsupials in the Central American Sub-region are represented by two genera containing about seven species, most of which are also found further south. One of these —the common opossum (Didelphys marsupialis)-extends northwards into the Nearctic Region as well as far southwards into Brazil, where, however, it has a slightly modified form.

The Edentates are well represented in the CentralAmerican Sub-region by two Sloths, three Ant-eaters, and an Armadillo, although the greater number of these are met with only in the most southern portion of the Subregion. The Armadillo (Tatusia novemcincta) is a widely spread species, ranging from Texas throughout the Subregion, and extending southwards to Paraguay.

Central America is also remarkable for possessing two out of the four American species of Tapir exclusively confined to it; these are Baird's Tapir (Tapirus bairdi), extending from Mexico to Panama, and Dow's Tapir (T. dowi), found only in Guatemala and Costa Rica.

Very few of the typical South American Hystricomorphine Rodents extend as far north as Central America. The greater number of the animals of this order found within Central American limits belong to the Sciurine and Murine groups, which have spread southwards from their homes in the Nearctic Region.

Passing on to the Carnivora, we find nearly all the genera of this order met with in the South American continent (amongst which are the Cats, Dogs, Racoons, and Weasels) also represented in this Sub-region. The only exceptions are Icticyon, a peculiar form of Wild Dog restricted to South-East Brazil, and the Bear (Ursus), a species of which is found in the Andes of Peru.

The Bats of Central America are fairly numerous, and nearly all belong to South American genera. A large proportion of them are referable to the Phyllostomatidæ, one of the characteristic Mammal-families of the Neotropical Region.

Finally, as regards the Monkeys, the Marmosets (Hapalide) appear to be represented only by a single species, which is an intruder into the extreme southern end of the Sub-region. Of the other family of American Monkeys (Cebide), about eight species, against a total of at least sixty found in the Guiano-Brazilian Sub-region, occur in the Central American Sub-region. Of these five are peculiar, or not yet ascertained to occur elsewhere.

The following table gives the statistics of the origin and distribution of the Central-American genera of Mammals. The “ Endemic” genera are those confined to this Subregion; the “ Nearctic” genera are those common to this Sub-region and the Nearctic Region; the “ Neotropical” genera are those common to this Sub-region and one or more of the other Sub-regions of the Neotropical Region;

American” designates those found in both the Neotropical and Nearctic Regions, and “Cosmopolitan” those met with also in the Old World.

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]
« AnteriorContinuar »