SECTION V.-THE CENTRAL AMERICAN SUB-REGION

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 (Hapalida) 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 (Cebidae), 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.

The inspection of this table will show at a glance that the Central-American Sub-region is predominantly "Neotropical" as regards its mammals, but has received a small immigration of Nearctic forms, and possesses only few endemic types.

SECTION VI.-THE GUIANO-BRAZILIAN SUB-REGION

This extensive area, in which is combined three of the Sub-regions usually allotted to Birds, is the largest and by far the richest of the four divisions of the Neotropical Region adopted in the present article. It extends from the Isthmus of Panama in the north to about 30° south latitude. But the southern frontier between this and the Patagonian Sub-region is very undecided, the Fauna of Uruguay and the northern part of the Argentine Republic containing forms characteristic of both Sub-regions. western boundary is formed by the well-watered and forest-clad western slopes of the Andes, the waterless eastern slopes, together with the western slopes of Peru and Bolivia from the neighbourhood of the Equator downwards, being referable to the fourth or Patagonian Sub-region.

The

The greater part of the Guiano-Brazilian Sub-region consists of forest, and the Mammalian fauna, though tolerably abundant, is not nearly so profuse as that of the Birds and Insects, which are here both developed in far greater luxuriance than in any other part of the world.

This Sub-region is more especially the home of the peculiar Platyrrhine monkeys, the arboreal Sloths, and other tree-loving Mammals.

Beginning at the bottom of the list, we find that nearly

all the twenty-four species of Opossums known from the New World are found within its limits. The peculiarly modified Water-opossum (Chironectes) occurs all over its area, but also extends into the Central-American Subregion.

Among the Edentates the Sloths are the most characteristic inhabitants of its forests. But two peculiar genera of Armadilloes (Xenurus and Priodon) are confined to this Sub-region, and several other species of this group occur there. All three genera of Ant-eaters are also here met with.

Rodents are very abundant in this Sub-region, but, with the exception of Squirrels (Sciurus), Vesper-mice (Hesperomys), Pouched mice (Heteromys), and a single Hare (Lepus), they all belong to the Hystricomorphine group, which is so highly developed in the Neotropical Region.

The Guiano-Brazilian Sub-region is also the special home of the Phyllostomine bats. Out of a total of about sixtyfive species of this family forty-four are found in this Sub-region, and the greater number of them are confined to it. Such, too, is the case with the Platyrrhine monkeys. The Marmosets (Hapalide) would be also unknown outside the limits of the Sub-region had not a single species, as already mentioned, overstepped the northern boundary at Panama. The Capuchins (Cebida), numbering more than sixty species and belonging to ten genera, are likewise abundant, and are found elsewhere only in the Central-American Sub-region.

The following table shows at a glance the numbers of (1) the "Endemic" genera of this Sub-region, i.e. those not found beyond its limits; (2) the "Neotropical " genera, i.e.