^28 . , Memoirs of the Indian Museum. [Voi,. I, 



. Aceording to these surmises, the Mala^^ Archipelago is only the 

 surviving western part of a formerly greater archipelago, the 

 middle part of which has dived into the sea, whilst the eastern part 

 has consolidated to form the compact Indian land-mass. 



The question now is, in what directions the different components of the Indian ter- 

 restrial Oligochœte fauna may have used this great archipelago. It is true we have to 

 forego the attempt to delineate these in a precise manner ; but we may state some 

 of the more general facts. It is probable that the Moniligastrids have used a path leading 

 directly from the Malay region to the South Indian Island across a bridge now sunk 

 beneath the Bay of Bengal. As stated above, these Oligochsetes probably did not use 

 the route through, Bengal around the Bay of Bengal. It is probable also that some genera 

 restricted to the South Indian region and showing near relations only to Australia, 

 viz., Notoscolex and Megascolex, have, at least in part, used a path now sunk beneath 

 the sea. On the other hand, those genera of the North Indian district which show 

 connections with Australia or even with New Zealand alone, have probably used a 

 path across the recent Malayan region. It is true that we have as yet found hardly 

 any relics of these genera, viz., Perionychella, Octochœtus and others, in the Burmo- 

 Malayan region. Perhaps Woodwardia hurkilli, MICHI^SN., from lyower Burma may 

 be regarded as such a relic in the marginal part of this region. Indeed, we can hardly 

 look for more frequent relics in this region, for it is the proper dominion of the 

 vigorous, phyletically youngest Megascolecine genus Pheretima, which certainly has 

 extirpated nearly all phyletically older and feebler genera with which it has come 

 in contact. The study of the geographical distribution of earthworms has brought to 

 light cases of such a dispossession or extirpation of older and feebler forms by more 

 vigorous younger ones. The older forms, then, survive only as relics in certain sepa- 

 rated localities, mostly islands or districts isolated by deserts, no longer accessible in 

 earlier periods, namely the periods of migration of the more vigorous yoimger 

 forms. 



The northern and western relations of our region now remain to be discussed. The 

 Central Asian region north of India seems to be totally bare of endemic terrestrial 

 Oligochaetes. We possess some data as regards Oligochsetes from Tibet, and all these 

 refer to peregrihe species, doubtless introduced by man. Even in Kashmir, so near to 

 the Western Himalayas, only peregrine Oligochaetes seem to occur. Perhaps we have to 

 include also the Punjab in this region devoid of endemic terrestrial Oligochœtes. The 

 nearest localities with endemic terrestrial Oligochaetes are Persia (Farsistan andChusistan 

 at the northern angle of the Persian Gulf) and Turkistan. These districts belong 

 to the proper dominion of the family Lumbricidœ. It is not quite certain whether 

 the lyumbricid of Bengal, Helodrilus indiens, MICHLSN., is really endemic in 

 Calcutta. Perhaps it may prove to be an outpost of the Lumbricidœ from the Perso- 

 Turkistan region. In every case this northward connection is a very feeble one. Some- 

 what more distinct but also not quite certain are the connections of the Western Indian 

 district, westwards towards tropical Africa (Eudichogaster and a scarce Dichogaster , 

 about which we cannot be quite certain, in Western India and the genus Dichogaster 



