466 Scientific Proceedings, Royal Dublin Society. 
one species of the cosmopolitan Lestes, and three species of the 
characteristic Xanthagrion, which is also found in Australia. 
Among the genera common to both hemispheres, Argia has 
the vast majority of its species Neotropical and Sonoran, but 
there is one species in South Africa, one in the Kurile Islands, off 
the east coast of Siberia, and one in the Moluccas. We may here 
have a genus which, richly represented in tropical America, is on 
the verge of extinction elsewhere. Iicronympha and Lestes are 
almost cosmopolitan. Enallagma and Cenagrion are widespread. 
Both are characteristically northern genera, but while the former 
is predominantly American, and has an Oriental, but no Australian, 
species, the latter is markedly Huropean, seems unknown in the 
Oriental region, but has ten species in the Sandwich Islands. 
Nehalennia has a discontinuous range over the Neotropical, Sonoran 
and Holarctic regions. LErythronuma, a characteristic Holarctie 
genus with two species in Chili, recalls the range of many other 
groups of animals. . 
Comparatively few widespread genera are confined to the old 
world. Copera is Oriental, Mascarene, and Manchurian; and 
Pseudagrion Oriental, Ethiopian, and Australian, entering the — 
southern Holarctic. Argiocnemis and Teinobasis are Mascarene, — 
Oriental, and Australian, while Agriocnemis, near allied to the — 
former, is Ethiopian also. 
Most of the fossil dragonflies of this sub-family are of Tertiay ! 
age, but a few are described from the Solenhofen rocks. It is — 
interesting that a genus (Megapodagrion), now entirely Neotropical, 
should be represented in the Eocene beds of Wyoming, recalling — 
the former northern range of many of the mammals now confined 
to Tropical America. 
In the annexed table I have given the number of genera of 
each sub-family occurring in or peculiar to the various regions and 
sub-regions. In this table large genera are reckoned as peculiar, 
even if they cross with one or two species, the frontiers of their - 
region into the neighbouring sub-region. The first numbers 
in each column indicate the genera occurring in the region or 
sub-region, the succeeding numbers (in brackets) indicate the 
peculiar genera. 
