36 
partly on account of its large size, partly by its reference to the 
Tectocoris genus, the only recent species of which occurs in the East 
Indies and down to Australia. 
All these forms unmistakeably point to a tropical climate in the 
Eocene period and thus confirm the estimate obtained by other ways, 
namely that the middle temperature of the Eocene period has been 
10 0 higher than that of our days. For the sake of completeness I 
shall add that none of all the other Diatom-earth forms are incom¬ 
patible with the Tropics. 
As will be seen from what has been said about the tropical 
occurrence of the recent allies of the Diatom-earth insects, these recent 
forms seem most likely to occur in East Asia, and especially in the 
East Indies where they are all to be found. Whether this fact is of 
any importance, and whether any consequence may be drawn from 
it, or not, I shall leave undecided. 
For conclusion I shall only point to the difference between the 
fauna of the Diatom-earth and the amber fauna. Surely the original 
countries of the amber and the Diatom-earth have not been far distant 
from each other, and at about the same latitude. The layers in 
which amber is found in Samland are, as well known, referred 
to the beginning of the Oligocène, but the origin of amber and the 
age of the fauna enclosed in amber are sometimes — though hypoth¬ 
etically — referred to the Eocene. The amber fauna, however, is of 
a specifically temperate appearance, it consists of the same types as 
we meet with in the North-and Central-european fauna of our days 1 ). 
The Diatom-earth bed fauna, on the other hand, is as above men¬ 
tioned just as specifically tropical, and the (lower) Eocene age of the 
Diatom-earth being certain, it is not likely that the amber fauna 
indicating a much cooler temperature also should belong to the 
Eocene. 
x ) even if more tropical forms may be found among them — as already 
indicated by Berendt (Org. Reste d. Bernst. I. p. 59). 
