10 PROCEEDINGS OF THE NATIONAL MUSEUM. vou. 62. 
with Ris that the genus Planaeschna may be retained, pending a 
critical revision of the Brachytron series as a whole. 
Genus CEPHALAESCHNA de Selys. 
Plate 1. fig. I. 
For lack of material and sufficiently full information it is a matter 
of impossibility to deal in a satisfactory manner with the species 
grouped as a matter of convenience in this genus. In his mono- 
graph Martin adopted the course of suppressing the genus altogether, 
and referred a number of species to the Palaearctic genus Caliaeschna 
de Selys. He had been anticipated in this to a certain degree by 
Foerster who in 1908 described a Malayan species, belonging to the 
Brachytron series as Caliaeschna laidlawi. I prefer to regard Cali- 
aeschna as a monotypic genus probably confined to Asia Minor, Persia, 
and neighboring countries, and to leave some at least of the other 
oriental members of the series in the Selysian genus. 
But I admit this is merely the expression of an opinion which has 
not much substantial backing behind it and I believe that it is very 
likely that those members of the series here referred to Cephalaeschna 
may in future be found to stand in two or possibly even more genera. 
The genus Cephalaeschna was defined by de Selys (1883) in his Syn- 
opsis, and accepted by Karsch (1891) in the Kritik. Karsch more- 
over added a second species to the genus, Cephalaeschna sikkima, 
the type being Cephalaeschna orbifrons de Selys. 
C. orbifrons has a simple dentigerous plate in the female; that of 
sikkima is said to be armed with a pair of pointed spinelike processes. 
In this respect acutifrons Martin resembles orbifrons. I have before 
me the female of an undetermined species (probably =Calaeschna 
lugubris Martin ? = Caliaeschna sikkima Karsch) in which the dentiger- 
ous plate of the female is like that of stkkima. 
Foerster’s species laidlawi, seems to me from his description to 
belong rather to the next genus Periacschna. Of masoni Martin, the 
female is unknown. 
There is evidently considerable difference in the venation of these 
species. That of acutifrons is very dense, that of the female before 
me comparatively open; both have the pterestigma braced. 
Cephalaeschna conspersa Tillyard has lately been assigned to a 
distinct genus Dendroaeschna, by its author. 
In reviewing the genus Cephalaeschna I have been influenced largely 
by the fact that de Selys regarded its type species as generically 
distinct from Caliaeschna. The latter has an unbraced pterostigma, 
the interorbital suture is relatively short, and the triangles especially 
of the hinder wings relatively very small. Due weight should, I think, 
be also given to the very different characters of the areas occupied 
by the two genera, the arid or at least droughty regions ranging from 
