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the sea, because we find existing species with an enormous range. The ancestors of the Amblyrhynchi must have come as early, probably, as the earliest birds; and the same powers of dispersal have spread them over every island. The two American genera of lizards, and the tortoises, are perhaps later immigrants. Latest of all were the snakes, which hardly differ from continental forms; but it is not at all improbable that these latter, as well as the peculiar American mouse, have been early human importations. Snakes are continually found on board native canoes whose cabins are thatched with palm leaves; and a few centuries would probably suffice to produce some modification of a species completely isolated, under conditions widely different from those of its native country. Land-shells, being so few and small, and almost all modifications of one type, are a clear indication of how rare are the conditions which lead to their dispersal over a wide extent of ocean; since two or three individuals, arriving on two or three occasions only during the whole period of the existence of the islands, would suffice to account for the present fauna. Insects have arrived much more frequently; and this is in accordance with their habits, their lower specific gravity, their power of flight, and their capacity for resisting for some time the effects of salt water,
We learn, then, from the fauna of these islands, some very important facts. We are taught that tropical land-birds, unless blown out of their usual course by storms, rarely or never venture out to sea, or if they do so, can seldom pass safely over a distance of 500 miles. The immigrants to the Galapagos can hardly have averaged a bird in a thousand years. We learn, that of all reptiles lizards alone have some tolerably effective mode of transmission across the sea ; and this is probably by means of currents, and in connection with floating vegetation. Yet their transmission is a far rarer event ihan that of land-birds ; for, whereas three female immigrants will account for the lizard population, at least eight or ten ancestors are required for the birds. Land serpents can pass over still inore rarely, as two such transmissions would have sufficed to stock the islands with their snakes; and it is not certain that either of these occurred without the aid of man.
It is doubtful whether mammals or batrachians have any means of passing, independently of man's assistance; the former having but one doubtfully indigenous representative, the latter none at all. The remarkable absence of all gay or conspicuous flowers in these tropical islands, though possessing a zone of fairly luxuriant shrubby vegetation, and the dependence of this phenomenon on the extreme scarcity of insects, has been already noticed at Vol. I. p. 461, when treating of a somewhat similar peculiarity of the New Zealand fauna and flora.
1. South Temperate America, or the Chilian Sub-region. This sub-region may be generally defined as the temperate portion of South America. On the south, it commences with the cold damp forests of Tierra del Fuego, and their continuation up the west coast to Chiloe and northward to near Santiago. To the east we have the barren plains of Patagonia, gradually changing towards the north into the more fertile, but still treeless, pampas of La Plata. Whether this sub-region should be continued across the Rio de la Plata into Uruguay and Entre-rios, is somewhat doubtful. To the west of the Parana it extends northward over the Chaco desert, till we approach the border of the great forests near St. Cruz de la Sierra. On the plateau of the Andes, however, it must be continued still further north, along the" paramos" or alpine pastures, till we reach 5° of South latitude. Beyond this the Andes are very narrow, having no double range with an intervening plateau; and although some of the peculiar forms of the temperate zone pass on to the equator or even beyond it, these are not sufficiently numerous to warrant our extending the sub-region to include them. Along with the high Andes it seems necessary to include the western strip of arid country, which is mostly peopled by forms derived from Chili and the south temperate regions.
Mammalia.—This sub-region is well characterised by the possession of an entire family of mammalia having Neotropical affinities—the Chinchillidæ. It consists of 3 genera—Chinchilla (2 sp.), inhabiting the Andes of Chili and Peru as far as 9° south latitude, and at from 8,000 to 12,000 feet altitude; Lagidium (3 sp.), ranging over the Andes of Chili, Peru, and South Ecuador,
from 11,000 to 16,000 feet altitude; and Lagostomus (1 sp.), the "viscacha,” confined to the pampas. between the Uruguay and Rio Negro. Many important genera are also confined to this subregion. Auchenia (4 sp.), including the domesticated llamas and alpacas, the vicugna which inhabits the Andes of Peru and Chili, and the guanaco which ranges over the plains of Patagonia and Tierra del Fuego. Although this genus is allied to the Old World camels, it is a very distinct form, and its introduction from North America, where the family appear to have originated, may date back to a remote epoch. Ursus ornatus, the “spectacled bear" of the Chilian Andes, is a remarkable form, supposed to be most allied to the Malay bear, and probably forming a distinct genus, which has been named Tremarctos. Four genera of Octodontidae are also peculiar to this sub-region, or almost so; Habrocomus (1 sp.) is Chilian ; Spolacopus (2 sp.) is found in Chili and on the east side of the southern Andes ; Octodon (3 sp.) ranges from Chili into Peru and Bolivia ; Ctenomys (6 sp.) from the Straits of Magellan to Bolivia, with one species in South Brazil. Dolichotis, one of the Cavies, ranges from Patagonia to Mendoza, and on the east coast to 37° S. latitude. Myopotamus (1 sp.), the coypu (Echimyidæ), ranges from 33° to 48° S. latitude on the west side of the Andes, and from the frontiers of Peru to 42° S. on the east side. Reithrodon and Acodon, genera of Muridæ, are also confined to Temperate South America; Toly. peutes and Chlamydophorus, two genera of armadillos, the latter very peculiar in its organization and sometimes placed in a distinct family, are found only in La Plata and the highlands of Bolivia, and so belong to this sub-region. Otaria, one of the "eared seals ” (Otariida), is confined to the coasts of this subregion and the antarctic islands. Deer of American groups extend as far as Chiloe on the west, and the Straits of Magellan on the east coast. Mice of the South American genera Hesperomys and Reithrodon, are abundant down to the Straits of Magellan and into Tierra del Fuego, Mr. Darwin having collected more than 20 distinct species. The following are the genera of Mammalia which have been observed on the shores of the Straits of Magellan, those marked * extending into Tierra del Fuego:
*Pseudalopex (two wolf-like foxes), Felis (the puma), Mephitis (skunks), Cervus (deer), * Auchenia (guanaco), *Ctenomys (tucutucu), * Reithrodon and * H esperomys (American mice).
Birds.- Three families of Birds are confined to this sub-region, - Phytotomidæ (1 genus, 3 sp.), inhabiting Chili, La Plata, and Bolivia; Chionidida (1 genus, 2 sp.) the “sheath-bills,” found only at the southern extremity of the continent and in Kerguelen's Island, which with the other antarctic lands perhaps comes best here; Thinocoridæ (2 genera, 6 species) an isolated family of waders, ranging over the whole sub-region and extending northward to the equatorial Andes. Many genera are also peculiar : 3 of Fringillidæ, and 1 of Icteridæ ; 9 of Dendrocolaptidæ, 6 of Tyrannidæ, 3 of Trochilidæ, and 4 of Pteroptochidæ,—the last four South American families. There is also a peculiar genus of parrots (Henicognathus) in Chili; two of pigeons (Metriopelia and Gymnopelia) confined to the Andes and west coast from Peru to Chili; two of Tinamous, Tinamotes in the Andes, and Calodromus in La Plata ; three of Charadriidæ, Phægornis, Pluvianellus, and Oreophilus; and Rhea, the American ostriches, inhabiting all Patagonia and the pampas. Perhaps the Cariamida have almost as much right here as in the last sub-region, inhabiting as they do, the “pampas” of La Plata and the upland “campos” of Brazil; and even among the wide-ranging aquatic birds, we have a peculiar genus, Merganetta, one of the duck family, which is confined to the temperate plateau of the Andes.
Against this extensive series of characteristic groups, all either of American type or very distinct forms of Old World families, and therefore implying great antiquity, we find, in mammalia and birds, very scanty evidence of that direct affinity with the north temperate zone, on which some naturalists lay so much stress. We cannot point to a single terrestrial genus, which is characteristic of the north and reappears in this south temperate region without also occurring over much of the intervening land. Mustela seems only to have reached Peru ; Lepus is isolated in Brazil; true Ursus does not pass south of Mexico. In birds, the northern groups rarely go further south than Mexico or the Columbian Andes ; and the only case of discontinuous
distribution we can find recorded is that of the genus of ducks, Camptolæmus, which has a species on the east side of North America and another in Chili and the Falkland Islands, but these, Professor Newton assures me, do not properly belong to the same genus. Out of 30 genera of land-birds collected on the Rio Negro in Patagonia, by Mr. Hudson, only four extend beyond the American continent, and the same exclusively American character applies equally to its southern extremity. No list appears to have been yet published of the land-birds of the Straits of Magellan and Tierra del Fuego. The following is compiled from the observations of Mr. Darwin, the recent voyage of Professor Cunningham, and other sources; and will be useful for comparison. TURDIDÆ
PICIDÆ 1. Turdus falklandicus.
*23. Campephilus magellanicus.
24. Picus lignarius. TROGLODYTIDÆ. 2. Troglodytes magellanicus.
25. Ceryle stellata. 3. Chrysomitris barbata.
TROCHILIDE *4. Phrygilus gayi.
26. Eustephanus galeritus. *5.
aldunatii. 6. fruticeti.
CONURIDA *7. xanthogrammus.
27. Conurus patagonus. 8. Zonotrichia pileata. ICTERIDE.
VULTURIDÆ. 9. Sturnella militaris.
28. Cathartes aura. 10. Curæus aterrimus.
29. Sarcorhamphus gryphus. HIRUNDINIDE.
FALCONIDÆ, 11. Hirundo meyeni.
30. Circus macropterus.
31. Buteo erythronotus. TYRANNIDE.
32. Geranoaëtus melanolencus. 12. Tænioptera pyrope.
33. Accipiter chilensis. 13. Myiotheretes rufiventris.
34. Cerchneis sparverius. 14. Muscisaxicola mentalis.
35. Milvago albogularis. 15. Centrites niger.
36. Polyborus tharus. 16. Anæretes parulus. 17. Elainea griseogularis.
37. Asio accipitrinus.
38. Bubo magellanicus. 18. Upucerthia dumetoria. *19. Cinclodes patagonicus.
39. Pholeoptynx cunicularia.
40. Glaucidium nana. *20.
fuscus. +21. Oxyurus spinicauda.
41. Syrnium rufipes. PTEROPTOCHIDE.
STRUTHIONIDÆ. *22. Scytalopus magellanicus.
42. Rhea darwinii, VOL. II.-4