410 INSECTS IN THE COAL FORMATION. 
Dale,* and also of the wing of a Corydalis, which 
will he noticed in our description of PI. 46". 
It is very interesting and important, to have 
discovered in the Coal formation fossil remains, 
which establish the existence of the great In- 
sectivorous Class Arachnidans, at this early 
period. It is no less important to have found also 
in the same formation the remains of Insects, 
which may have formed their prey. Had neither 
of these discoA^eries been made, the abundance 
of Land plants would have implied the probable 
abundance of Insects, and this probability would 
have involved also that of the contemporaneous 
existence of Arachnidans, to control their undue 
increase. All these probabilities are now reduced 
to certainty, and we are thus enabled to fill up 
what has hitherto appeared a blank in the history 
of animal life, from those very distant times wLen 
the Carboniferous strata were deposited. 
The Estuary, or Fresh-water formation of those 
strata of the Carboniferous series which contain 
shells of Unio, in Coalbrook Dale, and in other 
Coal basins, renders the presence of Insects and 
Arachnidans in such strata, easy of explanation ; 
they may have been drifted from adjacent lands, 
by the same torrents that transported the ter- 
* Our figures (PI. 46". Figs. 1. 2.) represent these fossils of 
their natural size. See description of this Plate for further de- 
tails respecting them. 
