1930 ] Wing Venation of the Odonata and Agnatha 263 
(as in may-flies) and almost fuses with it, but not entirely: 
by looking from above (partly), and in a cross-section the 
partition between the two veins is still distinct. The origin 
of RS from this turning-point of M, which sometimes has 
the form of a cross-vein, is not clear to us. RS arises here 
from the base of M just as in may-flies and one certainly 
should look upon such a manner of origin as a secondary 
appearance, even if this tendency was acquired very long 
ago, for it was already present in the dragon-flies of the 
Liassic and Jurassic. After this vein follows Cu (CuP) 
which forms in the Anisoptera and Anisozygoptera, soon 
after its origin, a more or less sharp curve or projection 
posteriorly, as in the suborder Ephemeroidea. This curve 
is still entirely distinct in the Agrionidss, which appear to 
be the continuation of the Anisozygoptera, and dissappears 
only in the species of Calopterygidse (by the “straighten- 
ing” of Cu and A) . 
Now, if we compare the relation of the longitudinal veins 
to the convexities and concavities in dragon-flies to that in 
may-flies, we will ascertain the identity of their distribu- 
tion, which was well explained by Redtenbacher. This cir- 
cumstance, certainly, proves once more the correctness of 
our comparison of RS in dragon-flies (=M of the authors) to 
RS in may-flies, etc. Cu (Cu+Cui of the authors) is concave, 
as in the may-flies, and the next vein after it, which consists 
of the “anal bridge”+Cu 2 of the authors, forms the same 
kind of projection and is just as “convex” as in Ephemero- 
idea Ulm. This vein is unquestionably A x , and Cu 3 of the 
authors is Cu 2 , and to be even more exact, it is CuP. In the 
majority of the Anisoptera, A 1 comes into contact with Cu 
after the projection, but such contact, which often changes 
into fusion, is also frequent in the Ephemeroidea. On the 
other hand, in the majority of Zygoptera and Anisozygoptera 
and many other Anisoptera (compare Fig. 6, wing of fossil 
Heterophlebia dislocata, with Fig. 7, hind wing of Phyllope- 
talia apicalis Seyls), A 2 does not come in contact with Cu 
and runs independently and almost parallel to Cu. In its 
general appearance of A 1 (Cu 2 of the authors) of the dragon- 
flies, especially such as the Gomphidse or Anisozygoptera, 
corresponds entirely to Ai of may-flies, analogously form- 
ing an arch towards the front and analogously sending a 
