4 
Psyche 
[March 
(1922). For that reason I consider the venation of the Fouqueidae, 
and to a lesser extent that of the Spilapteridae, as more primitive 
and much closer to the supposedly ancestral type than that of Dictyo- 
neuridae. Especially primitive, perhaps, are those genera with richly 
branched, convex and concave parts of M and Cu. 
The venation of the Dictyoneuridae is an extremely simplified one 
for the Palaeodictyoptera and provides little basis for differentiation 
of taxa. It is therefore necessary to study the specimens in as much 
detail as possible in order to obtain full information. From my 
study of the Commentry material I am of the opinion that differences 
in cell shape of the archedictyon, the detailed outline of the posterior 
margin on the wings and distribution of cross veins and of the 
archedictyon may be useful for taxonomy. Nevertheless, the classi- 
fication of isolated wings at both specific and generic levels is less 
satisfactory than in other families of the order. 
In the Dictyoneuridae, the postcostal area is differently developed 
from that of all other families of Palaeodictyoptera. Arising from 
the very base of C, a single postcostal vein follows along the subcosta 
and terminates shortly on this vein. Commonly in the Palaeo- 
dictyoptera this subcostal vein is directed obliquely towards the 
costa, delimiting a triangular area and giving rise to several fine 
twigs. In the Dictyoneuridae also the precostal strip is very pro- 
nounced and broad, extending over the first third of the wing. 
Examining the other more specialized families, such as Eugereonidae, 
Calvertiellidae and Archaemegaptilidae, we note that the postcostal 
vein is completely reduced ; on the other hand the precostal mem- 
branous strip is enlarged to form a true precostal area. The Dictyo- 
neuridae apparently show the way in which the postcostal area 
became reduced in favor of the precostal area in the more advanced 
and specialized families. There is no doubt that the precostal area 
is a “younger” feature than the postcostal area, which developed 
by radial evolution in some groups only. 
Thanks to Handlirsch’s reconstruction, published in numerous 
textbooks of entomology and palaeontology, Stenodictya lobatci is 
undoubtedly the most famous fossil insect known. Unfortunately, 
as this revisional study shows, no one feature given in Handlirsch’s re- 
construction is correct. In contrast to what he figures, the mouthparts 
of Stenodictya are actually modified for sucking, the head is pro- 
vided with a large clypeal region, the prothoracic lobes have a 
venation and a cross venation, the wings are more slender distally 
than represented, Rs has more numerous branches, the arche- 
