ON THE GEOGRAPHICAL DISTRIBUTION OF THE CHIROPTERA. 165 



Straits, at a time when more dry land existed in the northern parts of the 

 Pacific Ocean. Although Vesperugo serotinus is the only species known 

 with certainty to extend from the Palrearctic to the Nearctic region, yet 

 so close is the connection between many other Patearctic and Nearctic 

 species (between Vespertilio mystacinus and V. nitidus, Vesperugo abramus 

 and V. hesperus, Vesperugo borealis and V. propinquus, e.g.), that it is not 

 necessary to require long separation to account for the few specific dif- 

 ferences now noticeable. 



Of the eleven species which appear to be peculiar to the Paljearctic 

 region, both the species of Ehinolophidas are evidently very closely 

 related to Ethiopian forms ; and the Vespertilionida?, with the exception of 

 Plecotus auritus, and Synotus barbastellus, are also represented by nearly 

 allied forms in either the Ethiopian or Oriental regions. 



The Nearctic and Pala^arctic regions are therefore more characterised, 

 so far as their Chiropterous fauna, by the absence rather than by the 

 presence of peculiar genera and species. 



The remaining four regions, however, present a remarkable contrast in 

 this respect. Each region appears to be as well characterised by its 

 Chiroptera as by any other order of Mammalia. 



This is especially noticeable in the Neotropical region, which possesses 

 a very remarkable family, the Phyllostomida?, nowhere represented beyond 

 its limits ; also six peculiar genera of Emballonuridae (amounting to 75 

 per cent, of the genera of that family) ; and two of Vespertilionida?, 

 making in all 39 genera peculiar to this region. 



The Ethiopian region (excluding Madagascar and its islands) is cha- 

 racterised by that very remarkable genus of Pteropodidas, Epomophorus, 

 which stands so far apart from all other genera of this family ; also by 

 71 species of other genera, of which more than 90 per cent, are peculiar. 



Madagascar and adjoining islands, included by Mr. Wallace under the 

 name of the Malagasy subregion, although possessing some species 

 (Phyllorhina commersoiiii, Nyctinomus acetabulosus, Taphozous mauritianus, 

 Vesperugo minutus, e.g.) which are also found on the African continent, 

 has other species representing a genus of which the remaining representa- 

 tives are found in far distant continents. Thus, as I have remarked 

 when treating of the distribution of the Pteropodida?, the genus Tteropus 

 is well represented in Madagascar and adjoining islands, and in the 

 Oriental and Australian regions as far as the Navigator's Islands, although 

 not a single species extends into the continent of Africa. This genus 

 includes by far the largest and most highly organised species of Chiro- 

 ptera, which in number also amount to more than one-tenth of the whole 

 order ; and their remarkable distribution can only be accounted for by 

 adopting the hypothesis of the existence at a comparatively recent date 

 of a continent, or, more probably, of an archipelago of very closely con- 

 nected islands, in the wide space of ocean now separating Madagascar 

 from India and Australia. It is inconceivable that species to which a 

 narrow channel of less than 200 miles suffices to act as an effectual 

 barrier, could traverse thousands of miles of unbroken ocean in other 

 directions. 



Even if we suppose that their presence in Africa is prevented by some 

 cause unknown to us, still it is difficult to imagine species so slow in their 

 flight as those of this genus crossing a channel of even half the width 

 of that separating the Comoro Islands from the coast of Africa. But 

 Tteropus medius of India is so closely related to Pt. edwardsii of Mada- 



