288 



NA TURE 



[JANUARY 17, I9OI 



Siwalik fauna. This constituent of the Cisgangetic fauna it is 

 proposed to distinguish by the term Aryan. The other con- 

 stituent is composed of reptiles and batrachians and may be 

 termed the Dravidian element. The latter is well developed 

 in the south of the Peninsula and especially along the south- 

 west or Malabar coast, and in Ceylon, but it gradually dis- 

 appears to the northward, its northern limit, so far as is known 

 at present, not extending to the 20th parallel of north latitude. 

 It is probable that this is the oldest part of the Cisgangetic 

 fauna, and it may have inhabited the country since India was 

 connected by land with Madagascar and South Africa, across 

 what is now the Indian Ocean, in Mesozoic and early Cenozoic 

 times. The other two elements, the Indo-Malay or Oriental 

 and the Aryan, are probably later immigrants, and its wider 

 diffusion may indicate that the Indo-Malay element has in- 

 habited the Indian Peninsula longer than the Aryan has. 

 There appears some reason for regarding the Indo-Malay 

 portion of the fauna as dating in India from Miocene times and 

 the Aryan from Pliocene, whilst in the Pleistocene epoch the 

 proportion of Aryan to Indo-Malay types of mammals in India, 

 as shown by the fossil faunas of the Nerbudda and the Karnul 

 caves, was much larger than at thfe present day. 



There are some other peculiarities of the Indian Peninsula 

 fauna to which attention may be called. One of these is the 

 presence of genera and sometimes of species which are found on 

 both sides of the Bay of Bengal, but not in the Himalayas or 

 Northern India. A good example is afforded by the genus 

 Tragttlus, of which one species inhabits Ceylon and India 

 south of about 22° N. lat., whilst two others are found in 

 Southern Tenasserim and the Malay Peninsula. In Pliocene 

 times the genus inhabited Northern India. Another instance is 

 the lizard Liolepis guttatus, found in Burma and Arrakan and 

 also in South Canara on the west coast of India. Examples 

 amongst reptiles aie rather numerous. Moreover, whilst there 

 are numerous alliances between the animals of Peninsular India 

 and those of Africa, there are also some curious connections 

 between India and Tropical America, but these are chiefly 

 amongst invertebrates. Some, however, are found in reptiles. 

 It is probable that such Indo- American connections are vestiges 

 of older life than the Indo-African. They are, of course, 

 generally speaking, instances of animal groups once more 

 widely distributed, but now only preserved in a few favourable 

 tropical localities. 



(4) The forest area of the Himalayas belongs to the same 

 sub-region as Assam, Burma (except South Tenasserim), 

 Southern China, Tonquin, Siam and Cambodia, and to this 

 sub-region the term Transgangetic may be applied. It is dis- 

 tinguished from the Cisgangetic sub-region by the absence of 

 the animals already specified as characteristic of that area and 

 by the presence of the following, which are wanting in the 

 Indian Peninsula — Mammals : the families Simiidse, Procyon- 

 idae, Talpidre and Spalacidee, and the sub-family Gymnurinee, 

 besides numerous genera such as Pn'onodon, Helictis, Arcionyx, 

 Athertira, Neniorhaedus and Cemas. Birds : the families 

 Euryloemidce, Indicatoridje and Heliornithidse, the sub-family 

 Paradoxornithinse. Reptiles : Platysternidse and Anguidte. 

 Batrachians : Discophidse, Hylidas, Pejobatidae and Salaman- 

 dridse. 



The relations of the Himalayan fauna to that of Assam and 

 Burma on the one hand, and to that inhabiting the Peninsula of 

 India on the other, may be illustrated by the mammals with bats 

 omitted. Of forty-one genera occurring in the Himalayas, three 

 are not found in the hills south of Assam or in Burma, whilst 

 sixteen are wanting in the Cisgangetic region. It should be 

 remembered that a large number of the genera are widespread 

 forms. As the result is not in agreement with the views of 

 some who have written on the subject, the relations of species 

 have been examined. It results that eighty-one species of mam- 

 malia, belonging to the orders Primates, Carnivora, Insectivora, 

 Rodentia and Ungulata, are recorded from the forest regions of 

 the Himalayas. Of these two are doubtful, twenty-two are not 

 known to occur south of the Himalayan range in India or Burma, 

 twenty-one are wide ranging forms and are found in both Burma 

 and the Indian Peninsula, one ov\y {Hystrix leuaira)\s,covaxviOX^ 

 to the Himalayan forests and the Indian Peninsula, but does not 

 range east of the Bay of Bengal, whilst thirty-five are found in 

 the countries east of the Bay of Bengal but not in the Peninsula 

 south of the Ganges. Of the thirty-five, eight only range as far 

 as the hills south of the Assam Valley, sixteen to Burma proper, 

 and eleven to the Malay Peninsula and Archipelago. Of the 



NO. 1629, VOL. 6l\ 



twenty-two species not ranging south of the Himalayas a large 

 majority are either Holarctic species or belong to Holarctic 

 genera. 



The fauna of the Himalayan forest area is partly Holarctic, 

 partly Indo-Malay. It is remarkably poor, when compared 

 with the Cisgangetic and Burmese faunas, in reptiles and batra- 

 chians. It also contains but few peculiar genera of mammals • 

 and birds, and almost all the peculiar types that do occur have 

 Holarctic affinities. The Indo-Malay element in the fauna is 

 very richly represented in the Eastern Himalayas, and gradually 

 diminishes to the westward until in Kashmir and farther west 

 it ceases to be the principal constituent. These facts are consis- 

 tent with the theory that the Indo-Malay constituent of the 

 Himalayan fauna, or the greater portion of it, has migrated into 

 the mountains from the eastward at a comparatively recent 

 period. It is an important fact that this migration appears to 

 have been from Assam and not from the Peninsula of India. 



(5) Southern Tenasserim agrees best in its vertebrata with the 

 Malay Peninsula, and should be included in the Malayan sub- 

 region of the Indo-Malay region. 



There are several points left which require explanation. 

 There is the much greater richness of the Oriental constituent 

 in the Cisgangetic fauna to the southward in Malabar and 

 Ceylon, although this is far away from the main Oriental area, 

 and the ocurrence also in the southern part of the Peninsula of 

 various mammalian, reptilian and batrachian genera, such as 

 Loris, Traguhis, Draco, Liolepis and Ixtilus, which are repre- 

 sented in Burma and the Malay countries but not in the Hima- 

 layas or Northern India. In connection with this the limitation 

 of the Dravidian element to the south of India should also be re- 

 membered. Then there is the occurrence of certain Himalayan 

 species on the mountains of Southern India and Burma and 

 even farther south, but not in the intervening area. There is 

 also the predominance of the Western, or what I have proposed to 

 call the Aryan, element in the Pleistocene fauna of the Nerbudda 

 Valley, and of Karnul in the north of the Carnatic tract. Lastly , 

 we have to account for the apparently recent immigration of 

 Oriental types into the Himalayas. 



Whilst it is quite possible that other explanations may be 

 found, it is evident that all these peculiarities of the Indian fauna 

 may have been due to the Glacial epoch. The great terminal 

 moraines occurring at about 7000 feet in Sikhim and the occur- 

 rence of similar moraines and other indications of ice action at 

 even lower levels in the Western Himalayas clearly show that 

 the temperature of the mountain range must have been much 

 lower than at the present day, when no glacier in Sikhim is 

 known to descend below about 14,000 feet. 



During the coldest portion of the Glacial epoch, a large part 

 of the higher mountains must have been covered by snow and 

 ice, and the tropical Indo-Malay fauna which had occupied the 

 range, and which may have resembled that of the Indian 

 Peninsula more than is the case at present, must have been 

 driven to the base of the mountains or exterminated. The 

 Holarctic forms apparently survived in larger numbers. The 

 Assam Valley and the hill ranges to the southward would afford 

 in damp, sheltered, forest-clad valleys and hill slopes a warmer 

 refuge for the Oriental fauna than the open plains of Northern 

 India and the much drier hills of the country south of the 

 Gangetic plain. The Oriental types of the Peninsula generally 

 must have been driven southwards, and some of them, such as 

 Lorts and Tragulus, which must originally have been in touch 

 with their Burmese representatives, have never returned. It 

 was probably during this cold period that the ossiferous Nerbudda 

 beds and the deposits in the Karnul caves were accumulated. 

 The tropical damp-loving Dravidian fauna, if it inhabited 

 Northern India, must have been driven out of the country. 

 Unless the temperature of India and Burma generally under- 

 went a considerable diminution, it is not easy to understand 

 how plants and animals of temperate Himalayan types suc- 

 ceeded in reaching the hills of Southern India and Ceylon, 

 as well as those of Burma and the Malay Peninsula. . 



When the whole country became warmer again after the cold £ 

 epoch had passed away, the Transgangetic fauna appears to have ™ 

 poured into the Himalayas from the eastward. At the present 

 day the comparatively narrow Brahmaputra plain in Assam is 

 far more extensively forest-clad, especially to the eastward, than 

 is the much broader Gangetic plain of Northern India, and if, 

 as is probable, the same difference between the two areas existed 

 at the close of the Glacial epoch, it is easy to see how much 

 greater the facilities for the migration of a forest-haunting fauna 



