Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/313

 Rh a medium in which only one or two species of Insects are now supposed to live.

Had no indications of Insects been discovered in a fossil state, the presence in any strata, of Scorpions or Spiders, both belonging to families constructed to feed on Insects, would have afforded a strong a priori argument, in favour of the probability, of the contemporaneous existence of that very numerous class of animals, which now forms the prey of the Arachnidans. This probability has been recently confirmed by the discovery of two Coleoptera of the family Curculionidæ in the Iron-stone of Coalbrook Dale, and also of the wing of a Corydalis, which will be noticed in our description of Pl. 46″.

It is very interesting and (important, to have discovered in the Coal formation fossil remains, which establish the existence of the great Insectivorous 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 discoveries 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 when the Carboniferous strata were deposited.

The Estuary, or Freshwater formation of those strata of the Corboniferous 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