In the above list the species marked * extend to Tierra del Fuego. It is a remarkable fact that so many of the species belong to genera which are wholly Neotropical, and that the specially South American families of Icteridæ, Tyrannidæ, Dendrocolaptidæ, Pteroptochidæ, Trochilidæ, and Conuridæ, should supply more than one-third of the species; while the purely South American genusPhrygilus, should be represented by four species, three of which abound in Tierra del Fuego.
Plate XVI. A Scene in the Andes of Chili, with characteristic Animals.—The fauna of South Temperate America being most fully developed in Chili, we place the scene of our illustration in that country. In the foreground we have a pair of the beautiful little chinchillas (Chinchilla lanigera), belonging to a family of animals peculiar to the sub-region. There are only two species of this group, both confined to the higher Andes, at about 8000 feet elevation. Coming round a projecting ridge of the mountain, are a herd of vicunas (Auchenia vicugna), one of that peculiar form of the camel tribe found in South America and confined to its temperate and alpine regions. The upper bird is a plant-cutter (Phytotoma rara), of sober plumage but allied to the beautiful chatterers, though forming a separate family. Below, standing on a rock, is a plover-like bird, theThinocorus orbignianus, which is considered to belong to a separate family, though allied to the plovers and sheath-bills. Its habits are, however, more those of the quails or partridges, living inland in dry and desert places, and feeding on plants, roots, and insects. Above is a condor, the most characteristic bird of the high Andes.
Reptiles and Amphibia.—These groups show, for the most part, similar modifications of American and Neotropical forms, as those we have seen to prevail among the birds. Snakes do not seem to go very far south, but several South American genera of Colubridæ and Dendrophidæ occur in Chili; whileEnophrysis peculiar to La Plata, andCallorhinusto Patagonia, both belonging to the Colubridæ. The Elapidæ do not extend into the temperate zone; butCraspedocephalus, one of the Crotalidæ, occurs at Bahia Blanca in Patagonia (Lat. 40° S.)
Plate XVI.
THE CHILIAN ANDES, WITH CHARACTERISTIC ANIMALS.
THE CHILIAN ANDES, WITH CHARACTERISTIC ANIMALS.
Lizards are much more numerous, and there are several peculiar and interesting forms. Three families are represented; Teidæ by two genera—Callopistespeculiar to Chili, andAmeivawhich ranges over almost the whole American continent and is found in Patagonia;Geckotidæby four genera, two of which,—CaudiverberaandHomonota—are peculiar to Chili, whileSphærodactylusandCubinaare Neotropical, the former ranging to Patagonia, the latter to Chili; and lastly the American family Iguanidæ represented by eight genera, no less than six being peculiar, (or almost so,) to the South temperate region. These areLeiodera,DiplolæmusandProctrotretus, ranging from Chili to Patagonia;Leiolæmus, from Peru to Patagonia;Phrymaturus, confined to Chili, andPtygoderuspeculiar to Patagonia and Tierra del Fuego. The other two genera,OplurusandLeiosaurus, are common to Chili and tropical South America.
Tortoises appear to be scarce, a species ofHydromedusaonly being recorded. Of the Amphibia, batrachia (frogs and toads) alone are represented, and appear to be tolerably abundant, seventeen species having been collected by Mr. Darwin in this sub-region. Species of the South American generaPhryniscus,Hylaplesia,Telmatobius,Cacotus,Hylodes,Cyclorhamphus,Pleurodema,Cystignathus, andLeiuperus, are found in various localities, some extending even to the Straits of Magellan,—-the extreme southern limit of both Reptilia and Amphibia, except one lizard (Ptygoderus) found by Professor Cunningham in Tierra del Fuego. There are also four peculiar genera,Rhinodermabelonging to the Engystomidæ;AlsodesandNannophryneto the Bombinatoridæ;Opisthodelphysto the Hylidæ; andCalyptocephalusto the Discoglossidæ.
It thus appears, that in the Reptiles all the groups are typically American, and that most of the peculiar genera belong to families which are exclusively American. The Amphibia, on the other hand, present some interesting external relations, but these are as much with Australia as with the North temperate regions. The Bombinatoridæ are indeed Palæarctic, but a larger proportion are Neotropical, and one genus inhabits New Zealand. The Chilian genusCalyptocephalusis allied to Australian tropical genera.The Neotropical genera of Ranidæ, five of which extend to Chili and Patagonia, belong to a division which is Australian and Neotropical, and which has species in the Oriental and Ethiopian regions.
Fresh-water Fishes.—These present some peculiar forms, and some very interesting phenomena of distribution. The genusPerciliahas been found only in the Rio de Maypu in Chili; andPercichthys, also belonging to the perch family, has five species confined to the fresh waters of South Temperate America, and one far away in Java.Nematogenys(1 sp.) is peculiar to Chili;Trichomycterusreaches 15,000 feet elevation in the Andes,—both belonging to the Siluridæ;Chirodon(2 sp.), belonging to the Characinidæ, is peculiar to Chili; and several other genera of the same family extend into this sub-region from Brazil. The familyHaplochitonidæhas a remarkable distribution; one of its genera, Haplochiton (2 sp.), inhabiting Tierra del Fuego and the Falkland Islands, while the other,Prototroctes, is found only in South Australia and New Zealand. Still more remarkable isGalaxias(forming the family Galaxidæ), the species of which are divided between Temperate South America, and Australia, Tasmania, and New Zealand; and there is even one species (Galaxias attenuatus) which is found in the Chatham Islands, New Zealand, and Tasmania, as well as in the Falkland Islands and Patagonia.Fitzroya(1 sp.) is found only at Montevideo;Orestias(6 sp.) is peculiar to Lake Titicaca in the high Andes of Bolivia;Jenynsia(1 sp.) in the Rio de la Plata—all belonging to the characteristic South American family of the Cyprinodontidæ.
Insects.—It is in insects more than in any other class of animals, that we find clear indications of a not very remote migration of northern forms, along the great mountain range to South Temperate America, where they have established themselves as a prominent feature in the entomology of the country. The several orders and families, however, differ greatly in this respect; and there are some groups which are only represented by modifications of tropical forms, as we have seen to be almost entirely the case in birds and reptiles.
Lepidoptera.—The butterflies of the South Temperate Sub-region are not numerous, only about 29 genera and 80 species being recorded. Most of these are from Chili, which is sufficiently accounted for by the general absence of wood on the east side of the Andes from Buenos Ayres to South Patagonia. The families represented are as follows: Satyridæ, with 11 genera and 27 species, are the most abundant; Nymphalidæ, 2 genera and 8 species; Lemoniidæ, 1 genus, 1 species; Lycænidæ, 3 genera, 8 species; Pieridæ, 6 genera, 14 species; Papilionidæ, 2 genera, 8 species; Hesperidæ, 4 genera, 13 species. One genus of Satyridæ (Elina) and 2 of Pieridæ (EroessaandPhulia) are peculiar to Chili. The following are the genera whose derivation must be traced to the north temperate zone:—Tetraphlybia,Neosatyrus, and 3 allied genera of 1 species each, were formerly included underErebia, a northern and arctic form, yet having a few species in South Africa;Argyrophorus, allied toÆneis, a northern genus;Hipparchia, a northern genus yet having a species in Brazil;—all Satyridæ. The Nymphalidæ are represented by the typical north temperate genusArgynnis, with 7 species in Chili;Colias, among the Pieridæ, is usually considered to be a northern genus, but it possesses representatives in South Africa, the Sandwich Islands, Malabar, New Grenada, and Peru, as well as Chili, and must rather be classed as cosmopolitan. These form a sufficiently remarkable group of northern forms, but they are accompanied by others of a wholly Neotropical origin. Such areStibomorphawith 6 species, ranging through South America to Guatemala, andEteona, common to Chili and Brazil (Satyridæ);Apodemia(Lemoniidæ) confined to Tropical America and Chili.HesperocharisandCallidryas(Pieridæ), both tropical; andThracides(Hesperidæ) confined to Tropical America and Chili. Other genera are widely scattered; as,Epinephilefound also in Mexico and Australia;Cupido, widely spread in the tropics;Euryades, found only in La Plata and Paraguay, allied to South American forms ofPapilio, to the AustralianEurycus, and the northernParnassius; andHeteropterus, scattered in Chili, North America, and Tropical Africa. We find then, among butterflies, a large north-temperate element,intermingled in nearly equal proportions with forms derived from Tropical America; and the varying degrees of resemblances of the Chilian to the northern species, seems to indicate successive immigrations at remote intervals.
Coleoptera.—It is among the beetles of South Temperate America that we find some of the most curious examples of remote affinities, and traces of ancient migrations. The Carabidæ are very well represented, and having been more extensively collected than most other families, offer us perhaps the most complete materials. Including the Cicindelidæ, about 50 genera are known from the South Temperate Sub-region, the greater part from Chili, but a good number also from Patagonia and the Straits of Magellan. Of these more than 30 are peculiar, and most of them are so isolated that it is impossible to determine with precision their nearest allies.
The only remarkable form of Cicindelidæ isAgrius, a genus allied to theAmblycheilaandOmusof N.W. America. Two genera of Carabidæ,CascelliusandBaripus, are closely allied toPromecoderus, an Australian genus; and another,Lecanomerus, has one species in Chili and the other in Australia. Five or six of the peculiar genera are undoubtedly allied to characteristic Palæarctic forms; and such northern genera asCarabus,Pristonychus,Anchomenus,Pterostichus,Percus,Bradycellus,Trechus, andBembidium, all absent from Tropical America, give great support to the view that there is a close relation between the insects of the northern regions and South Temperate America. A decided tropical element is, however, present.Tropopterusis nearColpodes, a Tropical and South American genus;MimodromiusandPlagioteliumare nearCalleida, a South American genus; whilePachyteles,Pericompsus,Variopalpus, andCalleidaare widely spread American groups. The preponderance of northern forms seems, however, to be undoubted.
Six Carabidæ are known from Juan Fernandez, 3 being identical with Chilian species and 3 peculiar. As the island is 350 miles from the mainland, we have here a proof of how readily insects may be transported great distances.
The Palæarctic affinity of the South Temperate Carabidæ may be readily understood, if we bear in mind the great antiquity of the group, and the known long persistence of generic and specific forms of Coleoptera; the facility with which they may be transported to great distances by gales and hurricanes, either on land or over the sea; and, therefore, the probability that suitable stations would be rapidly occupied by species already adapted to them, to the exclusion of those of the adjacent tracts which had been specialised under different conditions. If, for example, we carry ourselves back to the time when the Andes had only risen to half their present altitude, and Patagonia had not emerged from the ocean (an epoch not very remote geologically), we should find nearly all the Carabidæ of South America, adapted to a warm, and probably forest-covered country. If, then, a further considerable elevation of the land took place, a large temperate and cold area would be formed, without any suitable insect inhabitants. During the necessarily slow process of elevation, many of the tropical Carabidæ would spread upwards, and some would become adapted to the new conditions; while the majority would probably only maintain themselves by continued fresh immigrations. But, as the mountains rose, another set of organisms would make their way along the highest ridges. The abundance and variety of the North Temperate Carabidæ, and their complete adaptation to a life on barren plains and rock-strewn mountains, would enable them rapidly to extend into any newly-raised land suitable to them; and thus the whole range of the Rocky Mountains and Andes would obtain a population of northern forms, which would overflow into Patagonia, and there, finding no competitors, would develope into a variety of modified groups. This migration was no doubt effected mainly, during successive glacial epochs, when the mountain-range of the Isthmus of Panama, if moderately increased in height, might become adapted for the passage of northern forms, while storms would often carry insects from peak to peak over intervening forest lowlands or narrow straits of sea. If this is the true explanation, we ought to find no such preponderant northern element in groups whichare proportionally less developed in cold and temperate climates. Our further examination will show how far this is the case.
Lucanidæ.—Only four genera are known in the sub-region. Two are peculiar,ChiasognathusandStreptocerus, the former allied to Tropical American, the latter to Australian genera; the other two genera are exclusively South American.
Cetoniidæ.—These seem very scarce, only a few species of the Neotropical genusGymnetisreaching Patagonia.
Buprestidæ.—These are rather numerous, many very beautiful species being found in Chili. Nineteen genera are represented in South Temperate America, and 5 of these are peculiar to it; 3 others are South American genera; 2 are Australian, and the remainder are wide-spread, but all are found also in Tropical America. The only north-temperate genus isDicerca, and even this occurs also in the Antilles, Brazil, and Peru. Of the peculiar genera, the largest,Dactylozodes(26 sp.), has one species in South Brazil, and is closely allied toHyperantha, a genus of Tropical America;Epistomentisis allied toNascis, an Australian genus;Tyndarisis close toAcmœodera, a genus of wide range and preferring desert or dry countries. The other two are single species of cosmopolitan affinities. On the whole, therefore, the Buprestidæ are unmistakeably Neotropical in character.
Longicorns.—Almost the whole of the South Temperate Longicorns inhabit Chili, which is very rich in this beautiful tribe. About 75 genera and 160 species are known, and nearly half of the genera are peculiar. Many of the species are large and handsome, rivalling in beauty those of the most favoured tropical lands. Of the 8 genera of Prionidæ 6 are peculiar, but all are allied to Tropical American forms exceptMicroplophorus, which belongs to a group of genera spread over Australia, Europe, and Mexico. The Cerambycidæ are much more abundant, and their affinities more interesting. Two (SyllitusandPseudocephalus) are common to Australia and Chili. Twenty-three are Neotropical; and among theseIbidion,Compsocerus,Callideriphus,Trachyderes, andXylocharis, are best represented. Twenty arealtogether peculiar, but most of them are more or less closely allied to genera inhabiting Tropical America. Some, as the handsomeCheloderusandOxypeltus, have no close allies in any part of the world.Holopterus, though very peculiar, shows most resemblance to a New Zealand insect.Sibylla,Adalbus, andPhantagoderus, have Australian affinities; whileCalydonalone shows an affinity for north-temperate forms. One species of the northern genus,Leptura, is said to have been found at Buenos Ayres.
The Lamiidæ are less abundant. Nine of the genera are Neotropical. Two (ApomecynaandExocentrus) are spread over all tropical regions. Ten genera are peculiar; and most of these are related to Neotropical groups or are of doubtful affinities. Only one,Aconopterus, is decidedly allied to a northern genus,Pogonochærus. It thus appears, that none of the Lamiidæ exhibit Australian affinities, although these are a prominent feature in the relations of the Cerambycidæ.
It is evident, from the foregoing outline, that the insects of South Temperate America, more than any other class of animals, exhibit a connection with the north temperate regions, yet this connection is only seen in certain groups. In Diurnal Lepidoptera and in Carabidæ, the northern element is fully equal to the tropical, or even preponderates over it. We have already suggested an explanation of this fact in the case of the Carabidæ, and with the butterflies it is not more difficult. The great mass of Neotropical butterflies are forest species, and have been developed for countless ages in a forest-clad tropical country. The north temperate butterflies, on the other hand, are very largely open-country species, frequenting pastures, mountains, and open plains, and often wandering over an extensive area. These would find, on the higher slopes of mountains, a vegetation and conditions suited to them, and would occupy such stations in less time than would be required to adapt and modify the forest-haunting groups of the American lowlands. In those groups of insects, however, in which the conditions of life are nearly the same as regards both temperate and tropical species, the superiornumber and variety of the tropical forms has given them the advantage. Thus we find that among the Lucanidæ, Buprestidæ, and Longicorns, the northern element is hardly perceptible. Most of these are either purely Neotropical, or allied to Neotropical genera, with the admixture, however, of a decided Australian element. As in the case of the Amphibia and fresh-water fishes, the Australian affinity, as shown by insects, is of two kinds, near and remote. We have a few genera common to the two countries; but more commonly the genera are very distinct, and the affinity is shown by the genera of both countries belonging to a group peculiar to them, but which may be of very great age. In the former case, we must impute some of the resemblance of the two faunas to an actual interchange of forms within the epoch of existing genera—a period of vast and unknown duration in the class of insects; while in the latter case, and perhaps also in many of the former, it seems more in accordance with the whole of the phenomena, to look upon most of the instances as survivals, in the two southern temperate areas, of the relics of groups which had once a much wider distribution. That this is the true explanation, is suggested by the numerous cases of discontinuous and scattered distribution we have had to notice, in which every part of the globe, without exception, is implicated; and there is a reason why these survivals should be rather more frequent in Australia and temperate South America, inasmuch as these two areas agree in the absence of a considerable number of otherwise cosmopolitan vertebrate types, and are also in many respects very similar in climatic and other physical conditions. The preponderating influence of the organic over the physical environment, as taught by Mr. Darwin, leads us to give most weight to the first of the above-mentioned causes; to which we may also impute such undoubted cases of survival of ancient types as the Centetidæ of the Antilles and Madagascar—both areas strikingly deficient in the higher vertebrate forms. The probable mode and time of the cross migration between Australia and South America, has been sufficiently discussed in our chapter on the Australian region, when treating of the origin and affinities of the New Zealand fauna.
Islands of the South Temperate Sub-region.
These are few, and of not much zoological interest. Tierra del Fuego, although really an island, is divided from the mainland by so narrow a channel that it may be considered as forming part of the continent. The guanaco (Auchenia huanaco) ranges over it, and even to small islands further south.
The Falkland Islands.—These are more important, being situated about 350 miles to the east of Southern Patagonia; but the intervening sea is shallow, the 100 fathom line of soundings passing outside the islands. We have therefore reason to believe that they have been connected with South America at a not distant epoch; and in agreement with this view we find most of their productions identical, while the few that are peculiar are closely allied to the forms of the mainland.
The only indigenous Mammals are a wolf-like fox (Pseudalopex antarcticus) said to be found nowhere else, but allied to two other species inhabiting Southern Patagonia; and a species of mouse, probably one of the American generaHesperomysorReithrodon.
Sixty-seven species of Birds have been obtained in these islands, but only 18 are land-birds; and even of these 7 are birds of prey, leaving only 11 Passeres. The former are all common South American forms, but one species,Milvago australis, seems peculiar. The 11 Passeres belong to 9 genera, all found on the adjacent mainland. Three, or perhaps four, of the species are however peculiar. These arePhrygilus melanoderus,P. xanthogrammus,Cinclodes antarcticus, andMuscisaxicola macloviana. The wading and swimming birds are of little interest, except the penguins, which are greatly developed; no less than eight species being found, five as residents and three as accidental visitors.
No reptiles are known to inhabit these islands.
Juan Fernandez.—This island is situated in the Pacific Ocean, about 400 miles west of Valparaiso in Chili. It is only a few miles in extent, yet it possesses four land-birds, excluding the powerful Accipitres. These areTurdus falklandicus;Anæretesfernandensis, one of the Tyrannidæ; and two humming-birds,Eustephanus fernandensisandE. galeritus. The first is a widespread South Temperate species, the two next are peculiar to the island, while the last is a Chilian species which ranges south to Tierra del Fuego. But ninety miles beyond this island lies another, called "Mas-a-fuero," very much smaller; yet this, too, contains four species of similar birds; one,Oxyurus mas-a-fueræ, allied to the wide-spread South TemperateO. spinicauda, andCinclodes fusus, a South Temperate species—both Dendrocolaptidæ; with a humming-bird,Eustephanus leyboldi, allied to the species in the larger island. The preceding facts are taken from papers by Mr. Sclater in theIbisfor 1871, and a later one in the same journal by Mr. Salvin (1875). The former author has some interesting remarks on the three species of humming-birds of the genusEustephanus, above referred to. The Chilian species,E. galeritus, is green in both sexes.E. fernandensishas the male of a fine red colour and the female green, though differently marked from the female ofE. galeritus.E. leyboldi(of Mas-a-fuera) has the male also red and the female green, but the female is more like that ofE. galeritus, than it is like the female of its nearer ally in Juan Fernandez. Mr. Sclater supposes, that the ancient parent form of these three birds had the sexes alike, as in the present Chilian bird; that a pair (or a female having fertilised ova) reached Juan Fernandez and colonised it. Under the action of sexual selection (unchecked by some conditions which had impaired its efficacy on the continent) the male gradually assumed a brilliant plumage, and the female also slightly changed its markings. Before this change was completed the bird had established an isolated colony on Mas-a-fuera; and here the process of change was continued in the male, but from some unknown cause checked in the female, which thus remains nearer the parent form. Lastly the slightly modified Chilian bird again reached Juan Fernandez and exists there side by side with its strangely altered cousin.
All the phenomena can thus be accounted for by known laws, on the theory of very rare accidental immigrations from themainland. The species are here so very few, that the greatest advocate for continental extensions would hardly call such vast causes into action, to account for the presence of these three birds on so small and so remote an island, especially as the union must have continued down to the time of existing species. But if accidental immigration has sufficed here, it will also assuredly have sufficed where the islands are larger, and the chances of reaching them proportionately greater; and it is because an important principle is here illustrated on so small a scale, and in so simple a manner as to be almost undeniable, that we have devoted a paragraph to its elucidation.
A few Coleoptera from Juan Fernandez present analogous phenomena. All belong to Chilian genera, while a portion of them constitute peculiar species.
Land-shells are rather plentiful, there being about twenty species belonging to seven genera, all found in the adjacent parts of South America; but all the species are peculiar, as well as four others found on the island of Mas-a-fuera.
III. Tropical North America, or the Mexican Sub-region.
This sub-region is of comparatively small extent, consisting of the irregular neck of land, about 1,800 miles long, which connects the North and South American continents. Almost the whole of its area is mountainous, being in fact a continuation of the great range of the Rocky Mountains. In Mexico it forms an extensive table-land, from 6,000 to 9,000 feet above the sea, with numerous volcanic peaks from 12,000 to 18,000 feet high; but in Yucatan and Honduras, the country is less elevated, though still mountainous. On the shores of the Caribbean Sea and Gulf of Mexico, there is a margin of low land from 50 to 100 miles wide, beyond which the mountains rise abruptly; but on the Pacific side this is almost entirely wanting, the mountains rising almost immediately from the sea shore. With the exception of the elevated plateaus of Mexico and Guatemala, and the extremity of the peninsula of Yucatan, the whole of Central America is clothed with forests; and as its surface is much broken up into hill and valley, and the volcanicsoil of a large portion of it is very fertile, it is altogether well adapted to support a varied fauna, as it does a most luxuriant vegetation. Although many peculiar Neotropical types are absent, it yet possesses an ample supply of generic and specific forms; and, as far as concerns birds and insects, is not perhaps inferior to the richest portions of South America in the number of species to be found in equal areas.
Owing to the fact that the former Republic of Mexico comprised much territory that belongs to the Nearctic region, and that many Nearctic groups extend along the high-lands to the capital city of Mexico itself, and even considerably further south, there is much difficulty in determining what animals really belong to this sub-region. On the low-lands, tropical forms predominate as far as 28° N. latitude; while on the cordilleras, temperate forms prevail down to 20°, and are found even much farther within the tropics.
Mammalia.—Very few peculiar forms of Mammalia are restricted to tropical North America; which is not to be wondered at when we consider the small extent of the country, and the facility of communication with adjacent sub-regions. A peculiar form of tapir (Elasmognathus bairdi) inhabits Central America, from Panama to Guatemala, and, withMyxomys, a genus of Muridæ, are all at present discovered.Bassaris, a remarkable form of Procyonidæ, has been included in the Nearctic region, but it extends to the high-lands of Guatemala.Heteromys, a peculiar genus of Saccomyidæ or pouched rats, inhabits Mexico, Honduras, Costa Rica, and Trinidad. Five genera of monkeys extend here,—Ateles,Mycetes,Cebus,Nyctipithecus, andSaimiris; the two former alone reaching Mexico, the last only going as far as Costa Rica. Other typical Neotropical forms areGalera, the tayra, belonging to the weasel family;Nasua, the coatimundi;Dicotyles, the peccary;Cercolabes, the tree porcupine;Dasyprocta, the agouti;Cælogenys, the paca;Cholœpus, andArctopithecus, sloths;Cyclothurus, an ant-eater;Tatusia, an armadillo; andDidelphys, oppossum. Of Northern forms,Sorex,Vulpes,Lepus, andPteromysreach Guatemala.
Birds.—The productiveness of this district in bird life, maybe estimated from the fact, that Messrs. Salvin and Sclater have catalogued more than 600 species from the comparatively small territory of Guatemala, or the portion of Central America between Mexico and Honduras. The great mass of the birds of this sub-region are of Neotropical families and genera, but these are intermingled with a number of migrants from temperate North America, which pass the winter here; with some northern forms on the high-lands; and with a considerable number of peculiar genera, mostly of Neotropical affinities.
The genera of birds peculiar to this sub-region belong to the following families:—Turdidæ (2 genera); Troglodytidæ (1 gen.); Vireonidæ (1 gen.); Corvidæ (2 gen.); Ampelidæ (1 gen.); Tanagridæ (1 gen.); Fringillidæ (2 gen.); Icteridæ (1 gen.); Formicariidæ (2 gen.); Tyrannidæ (2 gen.); Cotingidæ (1 gen.); Momotidæ (1 gen.); Trogonidæ (1 gen.); Trochilidæ (14 gen.); Conuridæ (1 gen.); Cracidæ (2 gen.); Strigidæ (1 gen.); in all 37 genera of land-birds. The Neotropical families that do not extend into this sub-region are, Pteroptochidæ; the sub-familyFurnariinæof the Dendrocolaptidæ; the sub-familyConophaginæof the Tyrannidæ; the sub-familyRupicolinæof the Cotingidæ; Phytotomidæ; Todidæ; Opisthocomidæ; Chionididæ; Thinocoridæ; Cariamidæ; Psophiidæ; Eurypygidæ; Palamedeidæ; and Struthionidæ. On the other hand Paridæ, Certhiidæ, Ampelidæ, and Phasianidæ, are northern families represented here, but which do not reach South America; and there are also several northern genera and species, of Turdidæ, Troglodytidæ, Mniotiltidæ, Vireonidæ, Fringillidæ, Corvidæ, Tetraonidæ, and Strigidæ, which are similarly restricted. Some of the most remarkable of the Neotropical genera only extend as far as Costa Rica and Veragua,—countries which possess a rich and remarkable fauna. Here only are found an umbrella bird, (Cephalopterus glabricollis); a bell bird (Chasmorhynchus tricarunculatus); and species ofDacnis(Cerœbidæ),Buthraupis,Eucometis,Tachyphonus(Tanagridæ),Xiphorhynchus(Dendrocolaptidæ);Hypocnemis(Formicariidæ);Euscarthmus(Tyrannidæ);Attila(Cotingidæ);Piprites(Pipridæ);Capito,Tetragonops(Megalæmidæ);Selenidera(Rhamphastidæ);Neomorphus(Cuculidæ);Monasa(Bucconidæ); many genera of Trochilidæ; andNothocercus(Tinamidæ); none of which extend further north. A considerable number of the peculiar genera noted above, are also found in this restricted area, which is probably one of the richest ornithological districts on the globe.
Reptiles.—These are much less known than the preceding classes, but they afford several peculiar and interesting forms. Snakes are perhaps the least remarkable; yet there are recorded 4 peculiar genera of Calamariidæ, 1 of Colubridæ, 1 of Homalopsidæ, 3 of Dipsadidæ; whileBoaandElapsare in common with South America. Lizards are much more specially developed.Chirotes, one of the Amphisbænians, is confined to Mexico and the southern part of the Nearctic region;Helodermaforming a peculiar family, Helodermidæ, is Mexican only;AbroniaandBarissia(Zonuridæ) are also Mexican, as isSiderolampusbelonging to the Scincidæ, whileBlepharactitis(same family) inhabits Nicaragua;Brachydactylus, one of the geckoes, is from Costa Rica; whilePhymatolepis,Lamanctus,Corytheolus,Cachrix,CorythophanesandChamæleopsis, all belonging to the Iguanidæ, are confined to various parts of the sub-region. In the same family we have also the Antillean,Cyclura, and the NearcticPhrynosomaandTropidolepis, as well as the wide-spread American genusAnolius.
Among the tortoises,Staurotypus, allied toChelydra, is found in Mexico and Guatemala; and another genus,Claudius, has been lately described from Mexico.
Amphibia.—These are chiefly Batrachians;Rhinophryna(forming a peculiar family) being confined to Mexico;Triprion, a genus of Hylidæ, inhabiting Yucatan, withLeylaandStrabomantis(Polypedatidæ) found only in Costa Rica and Veragua, are peculiar genera. The Salamandridæ, so abundant in the Nearctic region, are represented by a few species ofAmblystomaandSpelerpes.
Fresh-water fish.—Since the British Museum catalogue was published, a valuable paper by Dr. Günther, in the Transactions of the Zoological Society for 1868, furnishes much additional information on the fishes of Central America. In that part of the region south of Mexico, 106 species of fresh-water fishes areenumerated; and 17 of these are found in streams flowing into both the Atlantic and Pacific Oceans. On the whole, 11 families are represented among the fresh-water fish, and about 38 genera. Of these, 14 are specially Nearctic,—Amiurus(Siluridæ);Fundulus(Cyprinodontidæ);Sclerognathus(Cyprinidæ); andLepidosteus(Ganoidei). A much larger number are Neotropical; and several Neotropical genera, asHerosandPœcilia, are more largely developed here than in any other part of the region. There are also a considerable number of peculiar genera;—Petenia,Theraps, andNeotrophus(Chromides);Ælurichthys(Siluridæ);Chalcinopsis(Characniidæ);Characodon,Belonesox,Pseudoxiphophorus,Platypœcilus,Mollienesia, andXiphophorus(Cyprinodontidæ). A few peculiar Antillean forms are also present; asAgonostoma(Mugilidæ);GambusiaandGirardinuus(Cyprinodontidæ). The other families represented are Percidæ (1 genus); Pristopomatidæ (2 gen.); Gobiidæ (1 gen.); Clupeidæ (2 gen.); and Gymnotidæ (1 genus).
On the whole the fish-fauna is typically Neotropical, but with a small infusion of Nearctic forms. There are a considerable proportion of peculiar genera, and almost all the species are distinct from those of other countries. The predominant family is that of the Cyprinodontidæ, represented by 12 genera; and the genusHeros(Chromidæ) has here its maximum development, containing between thirty and forty species. Dr. Günther considers that a number of sub-faunas can be distinguished, corresponding to some extent, with the islands into which the country would be divided by a subsidence of about 2,000 feet. The most important of these divisions is that separating Honduras from Costa Rica, and as it also divides a very marked ornithological fauna we have every reason to believe that such a division must have existed during the latter portion of the tertiary epoch. We shall find some farther evidence of this division in the next class.
Insects.—The butterflies of various parts of Central America and Mexico, having been largely collected, offer us some valuable evidence as to the relations of this sub-region. Their general character is wholly Neotropical, about one half of theSouth American genera being found here. There are also a few peculiar genera, as,Drucina(Satyridæ);Microtia(Nymphalidæ);Eumæus(Lycænidæ); andEucheira(Pieridæ).Clothilda(Nymphalidæ) is confined to this sub-region and the Antilles. The majority of the genera range over the whole sub-region from Panama to Mexico, but there are a considerable number, comprising many of the most characteristic South American forms, which do not pass north of Costa Rica or Nicaragua. Such areLycorea,Ituna,Thyridia,Callithomia,OleriaandCeratina,—all characteristic South American groups of Danaidæ;PronophilaandDynastor(Satyridæ);Protogonius,Pycina,Prepona,Nica,EctimaandColænis(Nymphalidæ);EurybiaandMethonella(Nemeobiidæ);Hades, andPanthemos(Erycinidæ).
Coleoptera.—These present some interesting features, but owing to their vast number only a few of the more important families can be noticed.
Cicindelidæ.—The only specially Neotropical genera recorded as occurring in this sub-region, areCtenostomaandHiresia, both reaching Mexico.
Carabidæ.—Several genera are peculiar.Molobrusis found in all parts of the sub-region, whileOnychopterygia,Phymatocephalus, andAnisotarsusare Mexican only. There are about 20 South American genera, most of which extend to Mexico, and include such characteristic Neotropical forms asAgra,Callida,Coptodera,Pachyteles,Ardistomus,Aspidoglossa,Stenocrepis, andPelecium.
Lucanidæ.—Of this important family there is, strange to say, not a single species recorded in Gemminger and Harold's catalogue up to 1868! It is almost impossible that they can be really absent; yet their place seems to he, to some extent, supplied by an unusual development of the allied Passalidæ, of which there are five South American and six peculiar genera.
Cetoniidæ.—All the larger South American genera extend to Mexico, which country possesses 3 peculiar forms,Ischnoscelis,Psilocnemis, andDialithus; whileTrigonopeltastesis characteristic, having 4 Mexican, 1 Brazilian, and 1 North American species.
Buprestidæ.—In this family there are no peculiar genera. All the large South American groups are absent, the only important and characteristic genus beingStenogaster.
Longicorns.—This important group is largely developed, the country being well adapted to them; and their distribution presents some features of interest.
In the Prionidæ there are 6 peculiar genera, the largest beingHolonotuswith 3 species; two others,DerotrachusandMallaspis, are characteristic; 3 more are common to South America, and 1 to Cuba. The Cerambycidæ are much more numerous, and there are 24 peculiar genera, the most important beingSphenothecus,Entomosterna, andCyphosterna; whileCrioprosopusandMetaleptusare characteristic of the sub-region, although extending into South America; about 12 Neotropical genera extend to Mexico or Guatemala, while 12 more stop short, as far as yet known, at Nicaragua. Lamiidæ have a very similar distribution; 13 genera are peculiar, the most important beingMonilema,Hamatoderus, andCarneades, whilePhæaandLagochirusare characteristic. About sixteen typical Neotropical genera extend to Mexico, and 15 more only reach Nicaragua, among which are such important genera asAnisopus,Lepturgus, andCallia.
The land-shells are not sufficiently known to furnish any corresponding results. They are however mostly of South American genera, and have comparatively little affinity for those of the Antilles.
Relations of the Mexican sub-region to the North and South American Continents.—The sudden appearance of numerous South American forms of Edentata in temperate North America, in Post-Tertiary times, as narrated in Chapter VII., together with such facts as the occurrence of a considerable number of identical species of sea fish on the two sides of the Central American isthmus, render it almost certain that the union of North and South America is comparatively a recent occurrance, and that during the Miocene and Pliocene periods, they were separated by a wide arm of the sea. The low country of Nicaragua was probably the part submerged, leaving the highlands of Mexico and Guatemala still united with the NorthAmerican continent, and forming part of the Tertiary "Nearctic region." This is clearly indicated both by the many Nearctic forms which do not pass south of Nicaragua, of which the turkeys (Meleagris) are a striking example, and by the comparative poverty of this area in typical Neotropical groups. During the Miocene period there was not that marked diversity of climate between North and South America that now prevails; for when a luxuriant vegetation covered what are now the shores of the Arctic Ocean, the country south of the great lakes must have been almost or quite tropical. At an early Tertiary period, the zoological differences of the Nearctic and Neotropical regions were probably more radical than they are now, South America being a huge island, or group of islands—a kind of Australia of the New World, chiefly inhabited by the imperfectly organized Edentata; while North America abounded in Ungulata and Carnivora, and perhaps formed a part of the great Old World continent. There were also one or more very ancient unions (in Eocene or Miocene times) of the two continents, admitting of the entrance of the ancestral types of Quadrumana into South America, and, somewhat later, of the Camelidæ; while the isthmus south of Nicaragua was at one time united to the southern continent, at another made insular by subsidence near Panama, and thus obtained that rich variety of Neotropical types that still characterises it. When the final union of the two continents took place, the tropical climate of the lower portions of Guatemala and Mexico would invite rapid immigration from the south; while some northern forms would extend their range into and beyond the newly elevated territory. The Mexican sub-region has therefore a composite character, and we must not endeavour too rigidly to determine its northern limits, nor claim as exclusively Neotropical, forms which are perhaps comparatively recent immigrants; and it would perhaps be a more accurate representation of the facts, if we were to consider all the highlands of Mexico and Guatemala above the limits of the tropical forests, as still belonging to the Nearctic region, of which the whole country so recently formed a part.
The long-continued separation of North and South Americaby one or more arms of the sea, as above indicated, is further rendered necessary by the character of the molluscan fauna of the Pacific shores of tropical America, which is much more closely allied to that of the Caribbean sea, and even of West Africa, than to that of the Pacific islands. The families and many of the genera are the same, and a certain proportion of very closely allied or identical species, shows that the union of the two oceans continued into late Tertiary times. When the evidence of both land and sea animals support each other as they do here, the conclusions arrived at are almost as certain as if we had (as we no doubt some day shall have) geological proof of these successive subsidences.
Islands of the Mexican Sub-region.—The only islands of interest belonging to this sub-region, are Tres Marias and Socorro, recently investigated by Col. Grayson for some of the American Natural History societies.
Tres Marias consist of four small islands lying off the coast of north-western Mexico, about 70 miles from San Blas. The largest is about 15 miles long by 10 wide. They are of horizontally stratified deposits, of moderate height and flat-topped, and everywhere covered with luxuriant virgin forests. They appear to lie within the 100 fathom line of soundings. Fifty-two species of birds, of which 45 were land-birds, were collected on these islands. They consisted of 19 Passeres; 11 Picariæ (7 being humming-birds); 10 Accipitres; 2 parrots, and 3 pigeons. All were Mexican species except 4, which were new, and presumably peculiar to the islands, and one tolerably marked variety. The new species belong to the following genera;—ParulaandGranatellus(Mniotiltidæ);Icterus(Icteridæ); andAmazilia(Trochilidæ). A smallPsittaculadiffers somewhat from the same species on the mainland.
There are a few mammalia on the islands; a rabbit (Lepus) supposed to be new; a very small opossum (Didelphys), and a racoon (Procyon). There are also several tree-snakes, aBoa, and many lizards. The occurrence of so many mammalia and snakes is a proof that these islands have been once joined to the mainland; but the fact that some of the species of both birds andmammals are peculiar, indicates that the separation is not a very recent one. At the same time, as all the species are very closely allied to those of the opposite coasts when not identical, we may be sure that the subsidence which isolated them is not geologically remote.
Socorro, the largest of the Revillagigedo Islands, is altogether different from the Tres Marias. It is situated a little further south (19 S. Latitude), and about 300 miles from the coast, in deep water. It is about 2,000 feet high, very rugged and bare, and wholly volcanic. No mammalia were observed, and no reptiles but a small lizard, a new species of a genus (Uta) characteristic of the deserts of N.-Western Mexico. The only observed land-shell (Orthalicus undatus) also inhabits N.-W. Mexico. Only 14 species of birds were obtained, of which 9 were land-birds; but of these 4 were new species, one a peculiar variety, and another (Parula insularis) a species first found in the Tres Marias. With the exception of this bird and aButeo, all the land-birds belonged to differentgenerafrom any found on the Tres Marias, though all were Mexican forms. The peculiar species belonged to the generaHarporhynchus(Turdidæ);Troglodytes(Troglodytidæ);Pipilo(Fringillidæ);Zenaidura(Columbidæ); and a variety ofConurus holochrous(Psittacidæ).
The absence of mammals and snakes, the large proportion of peculiar species, the wholly volcanic nature of these islands, and their situation in deep water 300 miles from land,—all indicate that they have not formed part of the continent, but have been raised in the ocean; and the close relation of their peculiar species to those living in N.-Western Mexico, renders it probable that their antiquity is not geologically great.
The Cocos Islands, about 300 miles S.-W. of the Isthmus of Panama, are known to possess one peculiar bird, a cuckoo of theCoccyzustype, which is considered by some ornithologists to constitute a peculiar genus,Nesococcyx.
IV. The West Indian Islands, or Antillean Sub-region.
The West Indian islands are, in many respects, one of the most interesting of zoological sub-regions. In position theyform an unbroken chain uniting North and South America, in a line parallel to the great Central American isthmus; yet instead of exhibiting an intermixture of the productions of Florida and Venezuela, they differ widely from both these countries, possessing in some groups a degree of speciality only to be found elsewhere in islands far removed from any continent. They consist of two very large islands, Cuba and Hayti;[3]two of moderate size, Jamaica and Portorico; and a chain of much smaller islands, St. Croix, Anguilla, Barbuda, Antigua, Guadeloupe, Dominica, Martinique, St. Lucia, St. Vincent, Barbadoes, and Grenada, with a host of intervening islets. Tobago, Trinidad, Margarita, and Curaçao, are situated in shallow water near the coast of South America, of which they form part zoologically. To the north of Cuba and Hayti are the Bahamas, an extensive group of coral reefs and islands, 700 miles long, and although very poor in animal life, belonging zoologically to the Antilles. All the larger islands, and most of the smaller ones (except those of coral formation) are very mountainous and rocky, the chains rising to about 8,000 feet in Hayti and Jamaica, and to nearly the same height in Cuba. All, except where they have been cleared by man, are covered with a luxuriant forest vegetation; the temperature is high and uniform; the rains ample; the soil, derived from granitic and limestone rocks, exceedingly fertile; and as the four larger islands together are larger than Great Britain, we might expect an ample and luxuriant fauna. The reverse is however the case; and there are probably no land areas on the globe, so highly favoured by nature in all the essentials for supporting animal life, and at the same time so poor in all the more highly organised groups of animals. Before entering upon our sketch of the main features of this peculiar but limited fauna, it will be well to note a few peculiarities in the physical structure of the islands, which have an important bearing on their pasthistory, and will enable us to account for much that is peculiar in the general character of their natural productions.
If we draw a line immediately south of St. Croix and St. Bartholomew, we shall divide the Archipelago into two very different groups. The southern range of islands, or the Lesser Antilles, are, almost without exception, volcanic; beginning with the small detached volcanoes of Saba and St. Eustatius, and ending with the old volcano of Grenada. Barbuda and Antigua are low islands of Tertiary or recent formation, connected with the volcanic islands by a submerged bank at no great depth. The islands to the north and west are none of them volcanic; many are very large, and these have all a central nucleus of ancient or granitic rocks. We must also note, that the channels between these islands are not of excessive depth, and that their outlines, as well as the direction of their mountain ranges, point to a former union. Thus, the northern range of Hayti is continued westward in Cuba, and eastward in Portorico; while the south-western peninsula extends in a direct line towards Jamaica, the depth between them being 600 fathoms. Between Portorico and Hayti there is only 250 fathoms; while close to the south of all these islands the sea is enormously deep, from more than 1,000 fathoms south of Cuba and Jamaica, to 2,000 south of Hayti, and 2,600 fathoms near the south-east extremity of Portorico. The importance of the division here pointed out will be seen, when we state, that indigenous mammalia of peculiar genera are found on the western group of islands only; and it is on these that all the chief peculiarities of Antillian zoology are developed.
Mammalia.—The mammals of the West Indian Islands are exceedingly few, but very interesting. Almost all the orders most characteristic of South America are absent. There are no monkeys, no carnivora, no edentata. Besides bats, which are abundant, only two orders are represented; rodents, by peculiar forms of a South American family; and insectivora (an order entirely wanting in South America) by a genus belonging to a family largely developed in Madagascar and found nowhere else. The early voyagers mention "Coatis" and "Agoutis" as beingfound in Hayti and the other large islands, and it is not improbable that species allied toNasuaandDasyproctadid exist, and have been destroyed by the dogs of the invaders; though, on the other hand, these names may have been applied to the existing species, which do bear some general resemblance to these two forms.
The Chiroptera, or bats, are represented by a large number of species and by several peculiar genera. The American family of Phyllostomidæ or vampires, has six genera in the Antilles, of which three,Lonchorina,Brachyphylla, andPhyllonycteris, are peculiar, the latter being found only in Cuba. The Vespertilionidæ have four genera, of which one,Nycticellus, is confined to Cuba. There are six genera of Noctilionidæ, of which one,Phyllodia, is confined to Jamaica.
The Insectivora are represented by the genusSolenodon, of which two species are known, one inhabiting Cuba the other Hayti. These are small animals about the size of a cat, with long shrew-like snout, bare rat-like tail, and long claws. Their peculiar dentition and other points of their anatomy shows that they belong to the family Centetidæ, of which five different genera inhabit Madagascar; while there is nothing closely allied to them in any other part of the world but in these two islands.
Seals are said to be found on the shores of some of the islands, but they are very imperfectly known.
The rodents belong to the family Octodontidæ, or, according to some authors, to the Echimyidæ, both characteristic South American groups. They consist of two genera,Capromys, containing three or four species inhabiting Cuba and Jamaica; whilePlagiodontia(very closely allied) is confined to Hayti. A peculiar mouse, a species of the American genusHesperomys, is said to inhabit Hayti and Martinique, and probably other islands. ADasyproctaor agouti, closely allied to, if not identical with, a South American species, inhabits St. Vincent, St. Lucia, and Grenada, and perhaps St. Thomas, and is the only mammal of any size indigenous to the Lesser Antilles. All the islands in which sugar is cultivated are, however, overrun with European rats and mice, and it is not improbable that these may havestarved out and exterminated some of the smaller native rodents.
Birds.—The birds of the Antilles, although very inferior in number and variety to those of the mainland, are yet sufficiently abundant and remarkable, to offer us good materials for elucidating the past history of the country, when aided by such indications as geology and physical geography can afford.
The total number of land-birds which are permanent residents in the West India islands is, as nearly as can be ascertained from existing materials, 203. There are, in addition to this number, according to Prof. Baird, 88 migrants from North America, which either spend the winter in some of the islands or pass on to Central or South America. These migrants belong to 55 genera, and it is an interesting fact that so many as 40 of these genera have no resident representatives in the islands. This is important, as showing that this northern migration is probably a recent and superficial phenomenon, and has not produced any (or a very slight) permanent effect on the fauna. The migratory genera which have permanent residents, and almost always representative species, in the islands, are in most cases characteristic rather of the Neotropical than of the Nearctic fauna, as the following list will show;Turdus,Dendrœca,Vireo,Polioptila,Agelæus,Icterus,Contopus,Myiarchus,Tyrannus,Antrostomus,Chordeiles,Coccyzus,Columba. By far the larger part of these birds visit Cuba only; 81 species being recorded as occurring in that island, while only 31 have been found in Jamacia, 12 in Porto Rico and St. Croix, and 2 in Tobago and Trinidad. Setting aside these migratory birds, as having no bearing on the origin of the true Antillean fauna, we will discuss the residents somewhat in detail.
The resident land-birds (203 in number) belong to 95 genera and 26 families. Of these families 15 are cosmopolitan or nearly so—Turdidæ, Sylviidæ, Corvidæ, Hirundinidæ, Fringillidæ, Picidæ, Cuculidæ, Caprimulgidæ, Cypselidæ, Trogonidæ, Psittacidæ, Columbidæ, Tetraonidæ, Falconidæ, and Strigidæ; 5 are American only—Vireonidæ, Mniotiltidæ, Icteridæ, Tyrannidæ, Trochilidæ; 4 are Netropical only or almostexclusively—Cœrebidæ, Tanagridæ, Cotingidæ, Conuridæ; 1 is Antillean only—Todidæ; while 1—Ampelidæ—is confined (in the western hemisphere) to North America, and almost to the Nearctic region. Of the 95 genera, no less than 31, or almost exactly one-third, are peculiar; while of the 203 resident species, 177 are peculiar, the other 26 being all inhabitants of South or Central America. Considering how closely the islands approach the continent in several places—Florida, Yucatan, and Venezuela—this amount of speciality in such locomotive creatures as birds, is probably unexampled in any other part of the globe. The most interesting of these peculiar genera are the following: 4 of Turdidæ, or thrushes—1 confined to the large islands, 1 to the whole archipelago, while 2 are limited to the Lesser Antilles; 2 genera of Tanagridæ, confined to the larger islands; 2 of Trogonidæ, also confined to the larger islands; 5 of hummingbirds, 3 confined to the Greater, 1 to the Lesser Antilles; 2 of cuckoos, one represented in all the large islands, the other in Jamaica only; 2 of owls, one peculiar to Jamaica, the other represented in St. Croix, St. Thomas, Portorico, and Cuba; and lastly,Todus, constituting a peculiar family, and having representative species in each of the larger islands, is especially interesting because it belongs to a group of families which are wholly Neotropical—the Momotidæ, Galbulidæ, and Todidæ. The presence of this peculiar form, with 2 trogons; 10 species of parrots, all but one peculiar; 16 peculiar humming-birds belonging to 8 genera; a genus of Cotingidæ; 10 peculiar tanagers belonging to 3 genera; 9 Cœrebidæ of 3 genera; together with species of such exclusively Netropical genera asCœreba,Certhiola,Sycalis,Phonipara,Elainea,Pitangus,Campephilus,Chloronerpes,Nyctibius,Stenopsis,Lampornis,Calypte,Ara,Chrysotis,Zenaida,Leptoptila, andGeotrygon, sufficiently demonstrate the predominant affinities of this fauna; although there are many cases in which it is difficult to say, whether the ancestors of the peculiar genera or species may not have been derived from the Nearctic rather than from the Neotropical region.
The several islands differ considerably in their apparentproductiveness, but this is, no doubt, partly due to our knowledge of Cuba and Jamaica being much more complete than of Hayti. The species of resident land-birds at present known are as follows:—
If we count the peculiar genera of each island, and reckon as (½) when a genus is common to two islands only, the numbers are as follows:—Cuba 7½, Hayti 3½, Jamaica 8½, Portorico 1, Lesser Antilles 3½. These figures show us, that although Jamaica is one of the smaller and the most isolated of the four chief islands, it yet stands in the first rank, both for the number of its species and of its peculiar forms of birds,—and although this superiority may be in part due to its having been more investigated, it is probably not wholly so, since Cuba has also been well explored. This fact indicates, that the West Indian islands have undergone great changes, and that they were not peopled by immigration from surrounding countries while in the condition we now see them; for in that case the smaller and more remote islands would be very much poorer, while Cuba, which is not only the largest, but nearest to the mainland in two directions, would be immensely richer, just as it really is in migratory birds.
The number of birds common to the four larger islands is very small—probably not more than half a dozen; between 20 and 30 are common to some two of the islands (counting the Lesser Antilles as one island) and a few to three; but the great mass of the species (at least 140) are confined each to some one of the five islands or groups we have indicated. This is an amount of isolation and speciality, probably not to be equalled elsewhere, and which must have required a remarkable series of physical changes to bring about. What those changes probably were, we shall be in a better position to consider when we have completed our survey of the various classes of land animals.
Plate XVII.