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South America is, to some extent, peopled by Oriental and Pacific genera of shells. On the west coast there is hardly any coral, while on the east it is abundant, showing a difference of physical conditions that must have greatly influenced the development of mollusca. When these various counteracting influences are taken into consideration, the identity or close affinity of about 140 species and 40 genera on the two sides of the Isthmus of Panama becomes very important; and, combined with the fact of 48 species of fish (or 30 per cent. of those known) being identical on the adjacent coasts of the two oceans (as deterinined by Dr. Günther), render it probable that Central America has been partially submerged up to comparatively recent geological times. Yet another proof of this former union of two oceans is to be found in the fossil corals of the Antilles of the Miocene age, which Dr. Duncan finds to be more allied to existing Pacific forms, than to those of the Atlantic or even of the Caribbean Sea.
In the concluding part of this work devoted to geographical zoology, the sub-regions are arranged in the order best adapted to exhibit them in a tabular form, and to show the affinities of the several regions; but for our present purpose it will be best to take first in order that which is the most important and most extensive, and which exhibits all the peculiar characteristics of the region in their fullest development. We begin therefore with our second division.
II. Tropical South-America, or the Brazilian Sub-region. This extensive district may be defined as consisting of all the tropical forest-region of South America, including all the open p!...ns and pasture lands, surrounded by, or intimately associated with, the forests. Its central mass consists of the great forestplain of the Amazons, extending from Paranaiba on the north Ernest of Brazil (onz. 4W.) to Zamora, in the province of Loja lat. 4" ş., long 79° W.), hich up in the Andes, on the west ;a distance in a straight line of more than 2,500 English miles,
along the whole of which there is almost certainly) one continuous virgin forest. Its greatest extent from north to south, is from the mouths of the Orinooko to the eastern slopes of the Andes near La Paz in Bolivia and a little north of Sta. Cruz de la Sierra (lat. 18° S.), a distance of about 1,900 miles. Within this area of continuous forests, are included some open "campos," or patches of pasture lands, the most important being,—the Campos of the Upper Rio Branco on the northern boundary of Brazil; a tract in the interior of British Guiana ; and another on the northern bank of the Amazon near its mouth, and extending some little distance on its south bank at Santarem. On the northern bank of the Orinooko are the Llanos, or flat open plains, partly flooded in the rainy season; but much of the interior of Venezuela appears to be forest country. The forest again prevails from Panama to Maracaybo, and southwards in the Magdalena valley; and on all the western side of the Andes to about 100 miles south of Guayaquil. On the N.E. coast of Brazil is a tract of open country, in some parts of which (as near Ceara) rain does not fall for years together; but south of Cape St. Roque the coast-forests of Brazil commence, extending to lat. 30° S., clothing all the valleys and hill sides as far inland as the higher mountain ranges, and even penetrating up the great valleys far into the interior. To the south-West the forest country reappears in Paraguay, and extends in patches and partially wooded country, till it almost reaches the southern extension of the Amazonian forests. The interior of Brazil is thus in the position of a great island-plateau, rising out of, and surrounded by, a lowland region of ever-verdant forest. The Brazilian subregion comprises all this forest-country and its included open tracts, and so far beyond it as there exists sufficient woody vegetation to support its peculiar forms of life. It thus extends considerably beyond the tropic in Paraguay and south Brazil; while the great desert of Chaco, extending from 25° to 30° S., lat. between the Parana and the Andes, as well as the high plateaus of the Andean range, with the strip of sandy desert on the Pacific coast as far as to about 5° of south latitude, belong to south temperate America, or the sub-region of the Andes.
Having already given a sketch of the zoological features of the Neotropical region as a whole, the greater part of which will apply to this sub-region, we must here confine ourselves to an indication of the more important groups which, on the one hand, are confined to it, and on the other are absent; together with a notice of its special relations to other regions.
Mammalia.- Many of the most remarkable of the American monkeys are limited to this sub-region; as Lagothrix; Pithecia, and Brachyurus, limited to the great Amazonian forests; Eriodes to south-east Brazil; and Callithrix to tropical South America. All the marmosets (Hapalidae) are also confined to this sub-region, one only being found at Panama, and perhaps extending a little beyond it. Among other peculiar forms, are 8 genera of bats; 3 peculiar forms of wild dog; Pteronura, a genus of otters; Inia, a peculiar form of dolphin inhabiting the upper waters of the Amazon; tapirs of the genus Tapirus (a distinct genus being fourd north of Panama); 4 genera of Muridæ ; Ctenomys, a genus of Octodontidae; the whole family of Echimyidæ, or spiny rats, (as far as the American continent is concerned) consisting of 8 genera and 28 species ; Chatomys, a genus of Cercolabidæ; the capybara (Hydrochærus) the largest known rodent, belonging to the Caviidæ; the larger ant-eaters (Myrmecophaga); sloths of the genus Bradypus ; 2 genera of armadillos (Dasypodidae); and two peculiar forms of the opossum family (Didelphyidæ). No group that is typically Neotropical is absent from this sub-region, except such as are peculiar to other single sub-regions and which will be noticed accordingly. The occurrence of a solitary species of hare (Lepus braziliensis) in central Brazil and the Andes, is I'markable, as it is cut off from all its allies, the genus not being known to occur elsewhere on the continent further south than Costa Rica. The only important external relation indicated by the Mammalia of this sub-region is towards the Ethiopian region, 2 genera of Echimnyidæ, Aulacodes and Petromys, occurring in South and South-east Africa.
Plate I V. Characteristic Neotropical Mammalia. -Our illustratin represents a mountainous forest in Brazil, the part of South America where the Neotropical Mammalia are perhaps best
developed. The central and most conspicuous figure is the collared ant-eater, (Tamandua tetradactyla), one of the handsomest of the family, in its conspicuous livery of black and white. To the left are a pair of sloths (Arctopithecus flaccidus) showing the curious black spot on the back with which many of the species are marked, and which looks like a hole in the trunk of a tree; but this mark seems to be only found on the male animal. The fur of many of the sloths has a greenish tinge, and Dr. Seemann remarked its resemblance to the Tillandsia usneoides, or“ vegetable horsehair," which clothes many of the trees in Central America; and this probably conceals them from their enemies, the harpy-eagles. On the right are a pair of opossums (Didelphys azaræ), one of them swinging by its prehensile tail. Overhead in the foreground are a group of howling monkeys (Mycetes ursinus) the largest of the American Quadrumana, and the noisiest of monkeys. The large hollow vessel into which the hyoid bone is transformed, and which assists in producing their tremendous howling, is altogether unique in the animal kingdom. Below them, in the distance, are a group of Sapajou monkeys (Cebus sp.); while gaudy screaming macaws complete the picture of Brazilian forest life.
Birds.—A very large number of genera of birds, and some entire families, are confined to this sub-region, as will be seen by looking over the list of genera at the end of this chapter. We can here only notice the more important, and summarize the results. More than 120 genera of Passeres are thus limited, belonging to the following 12 families: Sylviidæ (1), Troglodytidæ (2), Cerebidæ (4), Tanagridæ (26), Fringillidæ (8), Icteridæ (5), Pteroptochidæ (3), Dendrocolaptidæ (12), Formicariidæ (16), Tyrannidæ (22), Cotingidæ (16), Pipridæ (10). Of the Picariæ there are 76 peculiar genera belonging to 9 families, viz., Picidæ (2), Rhamphastidæ (1), Cuculidæ (1), Bucconidæ (2), Galbulidæ (5), Momotidæ (2), Podargidæ (1), Caprimalgidæ (4) Trochilidæ (58). There are 3 peculiar genera of Psittaci, 8 of Gallinæ, the only genus of Opisthocomidæ, 3 of Accipitres, 1 of Rallidæ, Psophia and Eurypyga types of distinct families, and 1 genus of Ardeidæ, Palamedeidæ, and Anatidæ respectively. The preceding enumeration shows how very rich this sub-region