28 
Psyche 
[March 
variation in the specific standing of the groups during the 
several geological periods. Have the Mecoptera, for ex- 
ample, really been on the wane since the Lower Permian, 
or are the figures which indicate this without significance? 
To answer this question one might consider the correlation 
between the occurrence of the orders in the deposits of each 
horizon; if the percentages of each order even approxi- 
mately agreed, we should have positive evidence of the 
value of our percentages. But this would be a long and tedi- 
ous recital, so we must find another way of accomplishing 
similar results. Fortunately Handlirsch in 1908 included 
in his volume on fossil insects a list of the percentages of 
the orders, similar to the one which we have considered 
above. At that time there were 7651 species of fossil in- 
sects described. In 1920 Handlirsch again listed the per- 
centages in a similar way for the fossils known at that time, 
a total of 9302 species. Now there are approximately 10,- 
400 species of fossil insects recognized. That is to say, be- 
tween the years 1908 and 1920, 1651 species of insects were 
described; and between 1920 and 1930, a total of 1100 
more. These additional species represent the fossils that 
have been taken in new deposits, as well as those contained 
in new collections from previously known beds. A com- 
parison, therefore, between the percentages obtained in 
1908, 1910, and 1930, furnishes us with a means of deter- 
mining how closely fossils in new localities, new deposits, 
and additional collections agree with older records, and 
consequently a means of determining whether or not our 
figures have any significance. In table 3 these percentages 
are listed in parallel columns. We observe at once, of 
course, the blankness of the Permian record before the 1930 
column. This, as I have explained above, is due to the fact 
that practically no Permian collections had been worked 
before 1920. We have since found three widely separated 
Permian beds, each with a diversified fauna, and each suffi- 
ciently fossiliferous so that our total of Permian specimens 
is well over 7000. We cannot therefore check these Per- 
mian figures with earlier ones, to any extent. In 1908 
Handlirsch placed the Permian blattids at about 80%. This 
was because Sellards had described only the cockroaches of 
the Kansan Permian at that time ; in the 1920 column this 
