XV] ZOO-GEOGRAPHICAL DISTRIBUTION 299 



across Torres Straits into Queensland: Ictinus, Gynacaniha, 

 Heliaeschna, Tetrathemis, Lyriothemis, Potamarcha, Orthetrum, 

 Raphismia, Aethriamanta. The following genera appear to be 

 well enough established in both the Oriental region and the 

 tropical part of the Australian to be considered as dientogenic : 

 Anaciaeschna, Macromia, Metaphya, Nannophlebia, Diplacina, 

 Nesoxenia, Lathrecista, Agrionoptera , Brachydiplax, Neurothemis, 

 Zygonyx, Hydrobasileus, Macrodiplax, Zyxomma, Camacinia and 

 Rhyothemis. They are, however, all ectogenic for the Australian 

 Continent itself. This shews us how very different the faunas of 

 Papua and Australia proper really are. 



Aeschna brevistyla is common in temperate Australia, especially 

 in Tasmania. It also occurs in New Zealand. It seems to be 

 a remnant of an old Antarctic fauna. Species referable to the 

 Holarctic genus Somatochlora have been described from New 

 Zealand and Chili ; and the presence of the archaic Austropetalia 

 on the Blue Mountains may perhaps be a third link in this slender 

 chain of evidence. 



Census of the Odonata of the World. 



The census here given is based upon Kirby's Catalogue (1890) 

 and upon the Zoological Record^ up to May, 1913. For the 

 Ethiopian and Australian regions, the records are complete to 

 the end of 1914. For the Nearctic region, Muttkowski's Catalogue 

 (1910) was made the basis. In the case of the Libellulinae, 

 Corduliinae and Aeschninae, the census has been rearranged on 

 the basis of the Selysian Monographs on these groups by Bis and 

 Martin. By the introduction of the trinomial system in the 

 Libellulinae the number of species has been very considerably 

 reduced. A similar result may be expected in the Agrionidae, 

 and perhaps also in the Calopterygidae, when a similar modern 

 treatment is accorded to those subfamilies. 



The numbers in brackets placed after the generic totals indicate 

 the number of genera peculiar to, or entogenic in, the given region, 

 but does not include genera entogenic in more than one region. 

 The "Regional Percentage" gives a fairly reliable measure of 

 the ''self-containedness " of each region. It is calculated from 

 the ratio of genera in brackets to the total. 



