906 General Notes. [ December, 
of these six insects (Gerephemera, Homothetus, Xenoneura) 
have been shown to possess a very peculiar neuration, dissimilar 
from both carbeniferous and modern types. As will also be 
shown under'the tenth head, the dissimilarity of structure of all 
the devonian insects is much greater than would be anticipated ; 
yet all the features of neuration can be brought into perfect har- 
mony with the system laid down by Heer. 
“The earliest insects were hexapods, and as far as the record 
goes, preceded in time both arachnids and myriapods. 
“They were all Jower Heterometabola. 
“They are all allied or belong to the Neuroptera, using the 
word in its widest sense. 
“Nearly all are synthetic types of comparatively narrow 
range. 
“ Nearly all bear marks of affinity to the carboniferous Palzo- 
dictyoptera, either in the reticulated surface of the wing, its longi- 
tudinal neuration, or both. 
“ On the other hand they are often of more and not less com- 
plicated structure than most Palzodictyoptera. 
“ With the exception of the general statement under the fifth 
head they bear little special relation to carboniferous forms, hav- 
ing a distinct facies of their own. 
“The devonian insects were of great size, had membranous 
wings and were probably aquatic in early life. The last state- 
ment is simply inferred from the fact that all the modern types 
most nearly allied to them are now aquatic. 
“Some of the devonian insects are plainly precursors of exist- 
ing forms, while others seem to have left no trace. The best ex- 
amples of the former are Platephemera, an aberrant form of an 
existing family ; and Homothetus which, while totally different 
in the combination of its characters from anything known among 
living or fossil insects, is the only palæozoic insect possessing 
that peculiar arrangements of veins found at the base of the wings 
in Odonata typified by the arculus, a structure previously known 
only as early as the Jurassic. Examples of the latter are Gere- 
phemera, which has a multiplicity of simple parallel veins 
next the costal margin of the wing, such as no other insect an- 
cient or modern is known to possess; and Xenoneura, were the 
relationship of the internomedian branches to each other and to 
the rest of the wing is altogether abnormal. 
“If, too, the concentric ridges, formerly interpreted by me as 
possibly representing a stridulating organ, should eventually be 
proved an actual part of the wing, we should have here a struc- 
ture which has never since been repeated even in any modifie 
orm. 
“They show a remarkable variety of structure, indicating an 
abundance of insect life at that epoch. 
“The devonian insects also differ remarkably from all other 
