448 Scientific Proceedings, Royal Dublin Society. 
Holarctic, as well as to Papua. Zyamea is Neotropical, Sonoran, 
Hthiopian, Mascarene, Oriental, and Australian ; Rhyothemis has 
a somewhat similar range, but it extends into the southern Hol- 
arctic, while its presence in South America has only recently been 
made known by the discovery of a single species there. Sym- 
petrum is characteristically a northern genus; most abundant in 
Holarctic and Sonoran regions, it is sparingly represented in the 
Neotropical, Ethiopian, and Oriental, but is absent from Mada- 
gascar and the Australian Region. Tvrithemis is the most wide- 
spread genus of the sub-family, occurring in all the Neotropical, 
Ethiopian, Oriental and Australian sub-regions, as well as in 
Madagascar ; it has, however, but a single Sonoran species, and is 
only found in one Holarctic sub-region. Leptetrwm is common to 
the Holarctic, Sonoran, and Neotropical Regions, while Diplacodes 
is Neotropical, Sonoran, Ethiopian, and Oriental, one species 
entering the southern Holarctie. 
Among wide-ranging genera confined to the eastern hemi- 
sphere, we have Padpopleura which is Ethiopian, Mascarene, and 
Oriental. Uvrothemis has a similar but somewhat wider range, 
spreading north to the Mediterranean, and east to the Austro- 
Malayan sub-region. Deielia is Holarctic, Oriental, and Poly- 
nesian, having two species in China and Japan, and one in the 
Hawaian Islands. Zyxomma has characteristic species in West 
Africa, the Seychelles, India and Australia, Sumatra, and 
Papua. Orthetrwm occurs in all Holarctic sub-regions except 
the Canadian, in all Australian sub-regions except New Zea- 
land, and all over the Ethiopian, Mascarene, and Oriental 
Regions. It is a very variable genus with a large number of 
species exhibiting considerable diversity of structure, and appears 
therefore to be a dominant group in process of extension and 
development. Acisoma ranges all over the Ethiopian, Oriental, and 
Mascarene Regions, one species invading the southern Holaretie. 
Fossil dragonflies referred to the Libellulinee have been found 
in the Lower Purbeck of England, and the lithographic stone of 
Bavaria; these belong to the genera Aischnidium and Libelluiium. 
There are other fossil Libellulines from various Secondary and 
Tertiary deposits referred to ‘ Libed/ula,” but the generic name 
cannot stand for them in its modern, restricted sense. The 
Tertiary species outnumber the Secondary, and the comparatively 
large proportion of existing wide-ranging genera confirms the 
impression that the sub-family is still vigorous and developing. 
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