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Fresh-water fishes.—The great rivers of Tropical America abound in fish of many strange forms and peculiar types. Three families, and three sub-family groups are peculiar, while the number of peculiar genera is about 120. The peculiar families are Polycentridæ, with two genera ; Gymnotidæ, a family which includes the electric eels, (5 genera); and Trygonidæ, the rays, which are everywhere marine except in the great rivers of South America, where many species are found, belonging to two genera. Of the extensive family Siluridae, three sub-families Siluridæ anomalopteræ, S. Olisthopteræ, and S. branchiolæ, are confined to this region. The larger and more important of the peculiar genera are the following: Percilia, inhabiting Chilian, and Percichthys, South Temperate rivers, belong to the Perch family (Percidæ); Acharnes, found only in Guiana, belongs to the Nandidæ, a family of wide range in the tropics; the Chromidæ, a family of exclusively fresh-water fishes found in the tropics of the Ethiopian, Oriental, and Neotropical regions, are here represented by 15 genera, the more important being Acara (17 sp.), Heros (26 sp.), Crenicichla (9 sp.), Satanoperca (7 sp.). Many of these fishes are beautifully marked and coloured.
The Siluridæ proteropteræ are represented by 14'genera, of which Pimelodus (42 sp.), and Platystoma (11 sp.), are the most important; the Siluridæ stenobranchiæ by 11 genera, the chief being Doras (13 sp.), Auchenipterus (9 sp.), and Oxydoras (7 sp.). The Siluridæ proteropodes are represented by 16 genera, many of them being among the most singular of fresh-water fishes, clothed in coats of mail, and armed with hooks and serrated spines. The following are the most important, ---Chotostomus (25 sp.), Loricaria (17 sp.), Plecostonus (15 sp.) and Callichthys (11 sp.). The Characinidæ are divided between Tropical America and Tropical Africa, the former possessing about 40 genera and 200 species. The Haplochitonidæ are confined to South America and Australia ; the American genus being Haplochiton. The Cyprinodontidæ are represented by 18 genera, the most important being, Pacilia (16 sp.), Girardinus (10 sp.), and Gambusia (8 sp.) The Osteoglossidæ, found in Australian and African rivers, are represented in South America by the peculiar Arapaima, the “pirarucú” of the Amazon. The ancient Sirenoidei, also found in Australia and Africa, have the Lepidosiren as their American representative. Lastly, Ellipisurus is a genus of rays peculiar to the fresh waters of South America. We may expect these numbers to be largely increased and many new genera to be added, when the extensive collections made by Agassiz in Brazil are described.
Summary of Neotropical Vertebrates.—Summarizing the preceding facts, we find that the Neotropical region possesses no less than 45o families and more than 900 genera of Vertebrata which are altogether peculiar to it; while it has representatives of 168 families out of a total of 330, showing that 162 families are altogether absent. It has also representatives of 131 genera of Mammalia of which 103 are peculiar to it, a proportion of %; while of 683 genera of land-birds no less than 576 are peculiar, being almost exactly of the whole. These numbers and proportions are far higher than in the case of any other region.
The Neotropical region is so excessively rich in insect life, it so abounds in peculiar groups, in forms of exquisite beauty, and in an endless profusion of species, that no adequate idea of this branch of its fauna can be conveyed by the mere enumeration of peculiar and characteristic groups, to which we are here compelled to limit ourselves. Our facts and figures will, however, furnish data for comparison; and will thus enable those who have some knowledge of the entomology of any other country, to form a better notion of the vast wealth of insect life in this region, than a more general and picturesque description could afford them.
Lepidoptera.-The Butterflies of South America surpass those of all other regions in numbers, variety, and beauty; and we find here, not only more peculiar genera and families than elsewhere, but, what is very remarkable, a fuller representation of the whole series of families. Out of the 16 families of butterflies in all parts of the world, 13 are found here, and 3 of these are wholly peculiar—Brassolidæ, Heliconidæ, and Eurygonidæ, with a fourth, Erycinidæ, which only extends into the Nearctic 1 Ice Jacles and a. i. 6 si
region; so that there are 4 families peculiar to America. These four families comprise 68 genera and more than 800 species ; alone constituting a very important feature in the entomology of the region. But in almost all the other families there are numbers of peculiar genera, amounting in all to about 200, or not far short of half the total number of genera in the world(431). We must briefly notice some of the peculiarities of the several families, as represented in this region. The Danaidæ consist of 15 genera, all peculiar, and differing widely from the generally sombre-tinted fornis of the rest of the world. The delicate transparent-winged Ithomias of which 160 species are described, are the most remarkable. Melinæa, Napeogenes, Ceratina, and Dircenna are more gaily coloured, and are among the chief ornaments of the forests. The Satyridæ are represented by 25 peculiar genera, many of great beauty; the most remarkable and elegant being the genus Hætera and its allies, whose transparent wings are delicately marked with patches of orange, pink, or violet.
The genus Morpho is perhaps the grandest development of the butterfly type, being of immense size and adorned with the most brilliant azure tints, which in some species attain a splendour of metallic lustre unsurpassed in nature. The Brassolidæ are even larger, but are crepuscular insects, with rich though sober colouring. The true Heliconii are magnificent insects, most elegantly marked with brilliant and strongly contrasted tints. The Nymphalidæ are represented by such a variety of gorgeous insects that it is difficult to select. examples. Prominent are the genera Catagramma and Callithea, whose exquisite colours and symmetrical markings are unique and indescribable; and these are in some cases rivalled by Agrias and Prepona, which reproduce their style of coloration although not closely allied to them. The Erycinidæ, consisting of 59 genera and 560 species, comprise the most varied and beautiful of small butterflies; and it would be useless to attempt to indicate the unimaginable combinations of form and colour they present. It must be sufficient to say that nothing elsewhere on the globe at all resembles them. In Lycænidæ the worldwide genus Thecla is wonderfully developed, and the South
American species not only surpass all others in size and beauty, but some of them are so gorgeous on the under surface of their wings, as to exceed almost all the combinations of metallic tints we meet with in nature. The last family, Hesperidæ, is also wonderfully developed here, the species being excessively numerous, while some of them redeem the character of this generally sober family, by their rich and elegant coloration.
In the only other group of Lepidoptera we can here notice, the Sphingina, the Neotropical region possesses some peculiar forms. The magnificent diurnal butterfly-like moths, Urania, are the most remarkable; and they are rendered more interesting by the occurrence of a species closely resembling them in Madagascar. Another family of day-flying moths, the Castniidæ, is almost equally divided between the Neotropical and Australian regions, although the genera are more numerous in the latter. The American Castnias are large, thick-bodied insects, with a coarse scaly surface and rich dull colours; differing widely from the glossy and gaily coloured Agaristas, which are typical of the family in the East.
Coleoptera.- This is so vast a subject that, as in the case of the regions already treated, we must confine our attention to a few of the more important and best known families as representatives of the entire order.
Cicindelidæ. - We find here examples of 15 out of the 35 genera of these insects; and 10 of these genera are peculiar. The most important are Oxychila (11 sp.), Hiresia (14 sp.), and Ctenostoma (26 sp.). Odontochila (57 sp.) is the most abundant and characteristic of all, but is not wholly peculiar, there being a species in the Malay archipelago. Tetracha, another large genus, has species in Australia and a few in North America and Europe. The small genus Peridexia is divided between Brazil and Madagascar,-a somewhat similar distribution to that of Urania noticed above. One genus, Agrius, is confined to the southern extremity of the continent.
Carabidæ.-Besides a considerable number of cosmopolitan or wide-spread genera, this family is represented by more than 100 genera which are peculiar to the Neotropical region. The most important of these are Agra (150 sp.), Ardistohus (44 sp.), Schizogenius (25 sp.), Pelecium (24 sp.), Calophena (22 sp.), Aspidoglossa (21 sp.), and Lia, Camptodonotus, Stenocrepis, and Lachnophorus, with each more than 12 species. These are all tropical ; but there are also a number of genera (26) peculiar to Chili and South Temperate America. The most important of these are Antarctia (29 sp.), all except two or three confined to South Temperate America ; Scelodontis (10 sp.), mostly Chilian; Feronomorpha (6 sp.) all Chilian; and Tropidopterus (4 sp.), all Chilian. Helluomorpha (18 sp.), is confined to North and South America; Galerita, Callida, and Tetragonoderus, are large genera which are chiefly South American but with a few species scattered over the other tropical regions. Casnonia and Lebia are cosmopolite, but most abundant in South America. Pachyteles is mostly South American but with a few species in West Africa; while Lobodonotus has one species in South America and two in Africa.
Lucanidæ.—The Neotropical species of this family almost all belong to peculiar genera. Those common to other regions are Syndesus, confined to Tropical South America and Australia, and Platycerus which is Palæarctic and Nearctic, with one species in Brazil. The most remarkable genus is undoubtedly.Chiasognathus, confined to Chili. These are large insects of metallic green colours, and armed with enormous serrated mandibles. The allied genera, Pholidotus and Sphenognathus, inhabit Tropical South America. Streptocerus confined to Chili, is interesting, as being allied to the Australian Lamprima. The other genera present no remarkable features ; but Sclerognathus and Leptinoptera are the most extensive.
Cetoniidae.-These magnificent insects are but poorly represented in America; the species being mostly of sombre colours. There are 14 genera, 12 of which are peculiar. The most extensive genus is Gymnetis, which, with its allies Cotinis and Allorhina, form a group which comprehends two-thirds of the Neotropical species of the family. The only other genera of importance are, Inca (7 sp.), remarkable for their large size, and being the only American group in which horns are developed on the head;