Page images
PDF
EPUB

1 no

CUSES

1

Nunerous

munication between the Malay Islands, on the one hand, and South India with Ceylon, on the other. We find, for example, such typical Malay forms as the Tupaia, some Malay genera of cuckoos and Timalidze, some Malayan snakes and amphibia. The remarkable genus Testia among butterflies, and no less than seven genera of beetles of purely Malay type,' all occurring either in Ceylon only or in the adjacent parts of the Peninsula, but in no other part of India. These cases are so numerous and so important, that they compel us to assume some special geographical change to account for them. But directly between Ceylon and Malaya there intervenes an ocean-depth of more than 15,000 feet; and besides the improbability of so great a subsidence, of which we have no direct evidence, a land communication of this kind vould almost certainly have left more general proofs of its existence in the faunas of the two countries. But, when in Miocene times a sub-tropical climate extended into ('entral Europe, it seems probable that the equatorial belt of vegetation accompanied by its peculiar firuna, woulil have been widler than at present extending perhaps as far as Burma. If then the shallow northern part of the Bay of Bengal had been temporarily clevated during the late Miocene or Pliocene epochs, a few Malayan types may have migrated to the Peninsula of India ; and have been preserved only in Ceylon and the Nilgherries, where the climate still retains somewhat of its equatorial character and the struggle for existence is somewhat less serere than in the northern part of the region, which is so much more productive in varied forms of life.

For details see Geographical Distribution of Animals, vol. i. p. 327.

There are also indications hardly less clear, of some communication between India and Malaya on the one hand, and Maclagiiscar on the other ; but as these indications depend chiefly on resemblances in the birds and insects, they do not imply that any land connection has occurred. If, as seems probable, the Laccadive and Maldive Islands are the remains of a large island or indicate a western extension of India, while the Seychelles, with the shallow banks to the south-cast and the Chagos group are the remains of other extensive lands in the Indian Ocean, we should have a sufficient approximation of these outlying portions of the two continents to allow a certain amount of interchange of such winged groups as birds and insects, while preventing any intermixture of the mammalia.

The presence of some African types (and even some African species) of mammals in lindostan appears to be due to more recent changes, and may perhaps be explained by a temporary elevation of the comparatively shallow borders of the Arabian Sea, admitting of a land passage from North-East Africa to Western India.

There remains to be considered the supposed indications of a very ancient communication between Africa, Madagascar, Ceylon, Malaya, and Celebes, furnished by the occurrence over this extensive area of isolated forms of the Lemur tribe. The anomalous range of this group of animals has been thought to require for its explanation the existence of an ancient southern continent which has been called Lemuria, but a consideration of all the facts does not seem to warrant such a theory. Had such a continent ever existed we are sure that it must have lisappeared long before the Miocene period, or it would

assuredly have left more numerous and widespread indications of the former connections of these distant lands than actually exist. And when wc go back to the Eocene period we are met by the interesting discovery of an undoubtedly Lemurine animal in France, and what are supposed to be allied forms in North America. This proof of the great antiquity and wide range of lemurs is quite in accordance with their low grade of development; while the extreme isolation and specialization of many of the existing types (of which the Aye-aye of Madagascar is a wonderful example), and their scattered distribution over a wide tropical area, all suggest the idea that these are but the remnants of a once extensive and widely distributed group of animals, which, in competition with higher forms, have preserved themselves either by their solitary and nocturnal habits, or by restriction to ancient islands, like Madagascar, where the struggle for existence has been less severe. Lemuria, therefore, may be discarded as one of those temporary hypotheses which are useful for drawing attention to a group of anomalous facts, but which fuller knowledge shows to be unnecessary.

Regions of the New World.--- We will now pass across the Atlantic to the Western Ilemisphere, and consider first the Nearctic region, or temperate North America, whose present and past zoological relations with the rest of the world are of exceeding interest.

If we omit such animals as the musk-sheep (Ovibos), which is purely Arctic, and the peccaries (Dicotyles), which are hardly less distinctly tropical, the land. mammalia of North America are not very numerous; and they can be for the most part divided into two groups, the one allied to the Palusortic, and the other to the Neotropical fauna. The bears, the wolves, the cats, the bison, sherp and antelope, the hares, the marmots, and the pikas, resemble Palærctic forms; while the racoons, skunks, opossum, and resper-mice are now more peculiarly Vivtropical. There are also many genera which are altogether peculiar and characteristic of the region, as the prong-horn antelope (lotilocapra), the jumping-mouse (Jaculus), five genera of pouched rats (Saccomyida), the prairie dogs (Cynomy:-), the tree porcupines (Erethizon), and some others.

Birds present the same mixture of the two types; but the will turkeys (eleagris), the passenger pigeon (Eetopistes), the crested quails (Lophortys, &c.), the ruffed grouse (Cupidonia), and some other groups of less importance, are peculiar; while the family of the wood warblers (Wniotiltidze) is so largely developed that it may claim to be more characteristic of North than of South America.

Reptiles and Amphibia present a number of peculiar types; while no less than five peculiar families of freshwater fishes would alone serve to mark out this as distinct from every other part of the world.

Considering the evident affinity between the Nearctic and Palaarctic regions, there are here some curious deficiencies of groups which are common and widelyspread in the latter. Thus hedgehogs, wild horses and asses, swine, truc oxen, goats, dormice, and true mice are absent; while sheep and antelopes are only represented by solitary species in the Rocky Mountains.

DAV

more

Among birds, too, we have such striking deficiencies as the extensive families of flycatchers, starlings, and pheasants.

Turning now to the Neotropical region, comprising all South America and the tropical parts of the northern continent, we find that the Old World types have still further «liminished, while a number of new and altogether peculiar forms have taken their place. Insectivora have wholly disappeared with the exception of one anomalous form in the greater Antilles; bears are represented by one Chilian species; swine are replaced by peccaries; the great Bovine family are entirely unknown; the camel tribe are confined to the Southern Andes and the south temperate plains ; deer are not numerous; and all the varied Ungulata of the Old World are represented only by a few species of tapirs. These great gaps are, however, to some extent filleil up by a variety of interesting and peculiar types. Two families of monkeys (Cebida and Hipalida) differ in many points of structure from all the Quadrumana of the castern hemisphere. There is a peculiar family of bats--the vampyres; many peculiar weasels and Procyonidæ ; a host of peculiar rodents, comprising five distinct families, among which are the largest living forms of the order ; and a great number of Edentata, comprising the families of the sloths, armadillos, and ant-caters; and lastly, a considerable number of the marsupial family of opossums. As compared with the Old World, we find here a great abundance and variety of the lower types, with a corresponding scarcity of such higher forms as characterise the tropics of Africa and Asia.

« EelmineJätka »