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Psyche 
[June 
noted earlier, although ten of these are known from 
Paleozoic rocks, only one has a record which goes back to 
the Upper Carboniferous — the Blattaria or cockroaches. 
Their oldest remains are found in early Westphalian 
strata, which were deposited about two hundred forty 
million years ago. These first specimens consist only of 
wings, but complete or nearly complete specimens have 
been found in late Westphalian and Stephanian rocks. 
It is clear from these fossils that even that early in the 
earth’s history, the roaches were not very different from 
what they are now. They were flat, and had a broad pro- 
notum and tegminous wings like modern types. The 
venation, also, was similar to that which occurs in 
many of our living species — so much so that it is not 
easy to find obvious differences between Carboniferous 
and existing members of the group. Nymphal forms and 
several egg cases, which have been found in Permian 
rocks, serve to emphasize their similarity. Poaches are 
the most abundant of all Carboniferous insects. How- 
ever, this does not necessarily mean, as it has usually been 
interpreted, that they were the prevailing insects of the 
time ; it merely means that they were numerous in a par- 
ticular region or environment. Most insect-bearing rocks 
were first deposited as mud, and the roaches presumably 
thrived in moist or damp regions having a luxuriant 
plant growth. The picture we get from the fossils can 
therefore be misleading, for it gives us a conception of the 
local biota only ; if we had equally good samples of. the 
fauna of dry regions, we would probably find the roaches 
less numerous. The size of the Paleozoic roaches has also 
been erroneously described. Although the statement is 
often made that giant roaches lived in the Carboniferous, 
no fossil specimens have been found which exceed the size 
of some of our living species. It is true, of course, that 
the average size of fossil roaches exceeds that of the exist- 
ing species ; but that is because the large roaches had a 
better chance of being preserved as fossils than the small 
ones. This selective aspect of preservation is often over- 
looked. 
Let us now consider the existing orders which first 
