e or less closely allied species。 As an example； the Malayan bear is represented in North India by the Tibetan bear； both of which may be seen alive at the Zoological Society's Gardens。
The hoofed animals are twenty…two in number； of which about seven extend into Burmahand India。 All the deer are of peculiar species； except two； which range from Malacca into India。 Of the cattle； one Indian species reaches Malacca； while the Bos sondiacus of Java and Borneo is also found in Siam and Burma。 A goat…like animal is found in Sumatra which has its representative in India； while the two…horned rhinoceros of Sumatra and the single…horned species of Java； long supposed to be peculiar to these islands； are now both ascertained to exist in Burma； Pegu； and Moulmein。 The elephant of Sumatra； Borneo； and Malacca is now considered to be identical with that of Ceylon and India。
In all other groups of Mammalia the same general phenomena recur。 A few species are identical with those of India。 A much larger number are closely allied or representative forms； while there are always a small number of peculiar genera； consisting of animals unlike those found in any other part of the world。 There are about fifty bats； of which less than one…fourth are Indian species； thirty…four Rodents （squirrels； rats； &c。）； of which six or eight only are Indian； and ten Insectivora； with one exception peculiar to the Malay region。 The squirrels are very abundant and characteristic； only two species out of twenty…five extending into Siam and Burma。 The Tupaias are curious insect…eaters； which closely resemble squirrels； and are almost confined to the Malay islands； as；are the small feather…tailed Ptilocerus lowii of Borneo； and the curious long…snouted and naked…tailed Gymnurus rafllesii。
As the Malay peninsula is a part of the continent of Asia； the question of the former union of the islands to the mainland will be best elucidated by studying the species which are found in the former district； and also in some of the islands。 Now； if we entirely leave out of consideration the bats； which have the power of flight； there are still forty…eight species of mammals common to the Malay peninsula and the three large islands。 Among these are seven Quadrumana （apes； monkeys； and lemurs）； animals who pass their whole existence in forests； who never swim； and who would be quite unable to traverse a single mile of sea； nineteen Carnivora； some of which no doubt might cross by swimming； but we cannot suppose so large a number to have passed in this way across a strait which； except at one point； is from thirty to fifty miles wide； and five hoofed animals； including the Tapir； two species of rhinoceros； and an elephant。 Besides these there are thirteen Rodents and four Insectivora； including a shrew…mouse and six squirrels； whose unaided passage over twenty miles of sea is even more inconceivable than that of the larger animals。
But when we come to the cases of the same species inhabiting two of the more widely separated islands； the difficulty is much increased。 Borneo is distant nearly 150 miles from Biliton； which is about fifty miles from Banca； and this fifteen from Sumatra； yet there are no less than thirty…six species of mammals common to Borneo and Sumatra。 Java again is more than 250 miles from Borneo； yet these two islands have twenty…two species in common； including monkeys； lemurs； wild oxen； squirrels and shrews。 These facts seem to render it absolutely certain that there has been at some former period a connection between all these islands and the mainland； and the fact that most of the animals common to two or more of then； show little or no variation； but are often absolutely identical； indicates that the separation must have been recent in a geological sense； that is； not earlier than the Newer Pliocene epoch； at which time land animals began to assimilate closely with those now existing。
Even the bats furnish an additional argument； if one were needed； to show that the islands could not have been peopled from each other and from the continent without some former connection。 For if such had been the mode of stocking them with animals； it is quite certain that creatures which can fly long distances would be the first to spread from island to island； and thus produce an almost perfect uniformity of species over the whole region。 But no such uniformity exists； and the bats of each island are almost； if not quite； as distinct as the other mammals。 For example； sixteen species are known in Borneo； and of these ten are found in Java and five in Sumatra； a proportion about the same as that of the Rodents； which have no direct means of migration。 We learn from this fact； that the seas which separate the islands from each other are wide enough to prevent the passage even of flying animals； and that we must look to the same causes as having led to the present distribution of both groups。 The only sufficient cause we can imagine is the former connection of all the islands with the continent； and such a change is in perfect harmony with what we know of the earth's past history； and is rendered probable by the remarkable fact that a rise of only three hundred feet would convert the wide seas that separate them into an immense winding valley or plain about three hundred miles wide and twelve hundred long。 It may； perhaps； be thought that birds which possess the power of flight in so pre…eminent a degree； would not be limited in their range by arms of the sea； and would thus afford few indications of the former union or separation of the islands they inhabit。 This； however； is not the case。 A very large number of birds appear to be as strictly limited by watery barriers as are quadrupeds； and as they have been so much more attentively collected； we have more complete materials to work upon； and are able to deduce from them still more definite and satisfactory results。 Some groups； however； such as the aquatic birds； the waders； and the birds of prey； are great wanderers； other groups are little known except to ornithologists。 I shall therefore refer chiefly to a few of the best known and most remarkable families of birds as a sample of the conclusions furnished by the entire class。
The birds of the Indo…Malay region have a close resemblance to those of India； for though a very large proportion of the species are quite distinct； there are only about fifteen peculiar genera； and not a single family group confined to the former district。 If； however； we compare the islands with the Burmese； Siamese； and Malayan countries； we shall find still less difference； and shall be convinced that all are closely united by the bond of a former union。 In such well…known families as the woodpeckers； parrots； trogons； barbets； kingfishers； pigeons； and pheasants； we find some identical species spreading over all India； and as far as Java and Borneo； while a very large proportion are common to Sumatra and the Malay peninsula。
The force of these facts can only be appreciated when we come to treat the islands of the Austro…Malay region； and show how similar barriers have entirely prevented the passage of birds from one island to another； so that out of at least three hundred and fifty land birds inhabiting Java and Borneo； not more than ten have passed eastward into Celebes。 Yet the Straits of Macassar are not nearly so wide as the Java sea； and at least a hundred species are common to Borneo and Java。
I will now give two examples to show how a knowledge of the distribution of animals may reveal unsuspected facts in the past history of the earth。 At the eastern extremity of Sumatra； and separated from it by a strait about fifteen miles wide； is the small rocky island of Banca； celebrated for its tin mines。 One of the Dutch residents there sent some collections of birds and animals to Leyden； and among them were found several species distinct from those of the adjacent coast of Sumatra。 One of these was a squirrel （Sciurus bangkanus）； closely allied to three other species inhabiting respectively the Malay peninsula； Sumatra； and Borneo； but quite as distinct from them all as they are from each other。 There were also two new ground thrushes of the genus Pitta； closely allied to； but quite distinct from； two other species inhabiting both Sumatra and Borneo； and which did not perceptibly differ in these large and widely separated islands。 This is just as if the Isle of Man possessed a peculiar species of thrush and blackbird； distinct from the birds which are common to England and Ireland。
These curious facts would indicate that Banca may have existed as a distinct island even longer than Sumatra and Borneo； and there are some geological and geographical facts which render this not so improbable as it would at first seem to be。 Although on the map Banca appears so close to Sumatra； this does not arise from its having been recently separated from it； for the adjacent district of Palembang is new land； being a great alluvial swamp formed by torrents from the mountains a hundred miles distant。
Banca； on the other hand； agrees with Malacca； Singapore； and the intervening island of Lingen； in being formed of granite and laterite； and these have all most likely once formed an extension of the Malay peninsula。 As the rivers of Borneo and Sumatra have been for ages filling up the intervening sea； we may be sure that its depth has recently been greater； and it is very probable that those large islands were never directly connected with each other except through the Malay peninsula。 At that period the same species of squirrel and Pitta may have inhabited all these countries； but when the subterranean disturbances occurred which led to the elevation of the volcanoes of Sumatra； the small island of Banca may have been separated first； and its productions being thus isolated might be gradually modified before the separation of the larger islands had been completed。
As the southern part of Sumatra extended eastward and formed the narrow straits of Banca； many birds and insects and some Mammalia would cross from one to the other； and thus produce a general similarity of productions； while a few of the older inhabitants remained； to reveal by their distinct forms； their different origin。 Unless we