70 
Psyche 
[June 
previously mentioned (Protodonata and Protorthoptera), 
as well as the extinct order Palseodictyoptera and the 
existing order Blattaria or cockroaches. In the upper 
half of the Westphalian stage (C and D), about 15 million 
years after the first record of the insects, we come to the 
level of the Mazon Creek nodules in Illinois, second only 
to the Commentry shales in France as a source of Carbon- 
iferous insects. From this part of the Westphalian more 
than four hundred insects are known, representing the 
four orders already mentioned and in addition two other 
extinct ones, the Megasecoptera and Caloneurodea. From 
the Stephanian stage, which includes the Commentry de- 
posit, about fifteen hundred species have been described, 
belonging to the orders previously mentioned as well as 
still another exinct one, the Protohemiptera. Thus, we 
see that by the end of the Upper Carboniferous seven 
orders of insects had come into existence, of which one, 
the Blattaria, survived for some two hundred forty mil- 
lion years to the present time. 4 
Let us now continue into the Permian Period (Figure 
2), which represents an interval of about twenty-five mil- 
lion years. In the lower or oldest strata of the period 
eight orders have been found in addition to the seven 
which have persisted from the Carboniferous. Two of 
these, the Protoperlaria and Protelytroptera, are extinct, 
hut the others are living orders. These are the Ephem- 
erida, Odonata, Corrodentia, Hemiptera, Mecoptera, and 
Neuroptera. This fauna was an extremely interesting 
one, combining as it did eight extinct and seven existing 
orders. The Lower Permian was the last time, so far 
as our records now show, that the extinct orders out- 
numbered the existing ones. In Middle Permian rocks, 
Thysanoptera and Perlaria have been found ; and in upper 
Permian strata the Coleoptera appear. These make a 
total of eighteen living and extinct orders of insects which 
came into existence before the end of the Paleozoic era, 
about two hundred million years ago ; and of these ten are 
still living. 
4 I have not included in this account several extinct orders which are based 
upon very fragmentary specimens. 
