new Genus and Species of Odonata. 233 
published another species of Oploneschna (O. lapidaria) from 
Florissant (Proc. U.S. Nat. Mus. xlv. p. 577, 1913). 
The nearest relatives of Zrieschna are to be found among 
the Auschnine of the present day, rather than among the 
Miocene species which we have just considered. In the 
linear arrangement of the subfamily proposed by Dr. E. M. 
Walker, it would seem to find its proper place as a member of 
the Brachytron group of genera, and of the Brachytron series 
in that group (‘N. Amer. Dragonf. Genus Aislina,’ p. 25, 
1912). Litheschna, also, alone of the Miocene forms, appa- 
rently belongs to the Brachytron group, although not to the 
same series. The phylogenetic tree on p. 24 of the work cited 
shows the great branch formed by this group as ending with 
three twigs, representing the closely-allied genera Brachytron 
(Europe and Asia Minor), Hpteschna (North America), and 
Aischnophlebia (Japan). With these Holarctic genera 
Trieschna may be fittingly associated ; but, even at the first 
glance, it is seen to differ from them by reason of the 
narrowness of the fore-wing. The antenodals, too, are far 
more numerous, Triwschna possessing 33 of those cross-veins, 
as compared with 13-15 in Brachytron, 21-23 in Epieschna, 
and 18-24 in Aschnophlebia (R. Martin, Coll. Selys, Ausch., 
fasc. xix. pp. 86, 129, 139-140, 1909). Of greater signifi- 
eance still is the fact that in 77z@schna there are as many as 
three rows of cells between the radial sector and the radial 
supplement, instead of two rows, as in Aischnophlebia and 
pieschna, or one row only, asin Brachytron. In Trieschna 
the pterostigma is of moderate length, and is distinctly, if 
weakly, braced, whereas in Brachytron and Aéschnophlebia it 
is very long and not braced at all. Trteschna may be further 
differentiated from A¥schnophlebia by the subcosta not being 
prolonged beyond the nodus. In Epiceschna heros, Fabr., it 
is evident that we have a very near relative of Trieschna 
gossi, and the resemblance between them is unmistakable, 
not only as regards general plan, but also in respect of such 
characters as the shape of the triangle, the presence of three 
rows of cells between M, and the median supplement, and the 
retracted position, reduced length, and undecided bracing of 
the pterostigma. Nevertheless, as we have seen, there are 
differences of importance, and the narrowness of the fork of 
the radial sector in Triewschna may be added to the other 
distinguishing characters to which attention has been directed. 
Tn conclusion, it may be pointed out that the Bournemouth 
fossil indicates a dragonfly of great size, surpassing in alar 
expanse any species now occurring in the British Isles, as 
