INSECTS IN THE COAL FORMATION. 309 



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 

 Curculionidse in the Iron-stone of Coalbrook Dale,* and 

 also of the wing of a Corydalis, which will be 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 ex- 

 istence 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 probabilit} 

 would have involved also that of the contemporaneous exist- 

 ence 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 Fresh-water formation of those strata of 

 the Corboniferous series which contain shells of Unio, in 

 Coalbrook Dale, and in other Coal basins, renders the pre- 

 sence of Insects and Ai-achnidans in such strata, easy of 

 explanation; they may have been drifted from adjacent 



* Our figures (PI. 46". Figs. 1. 2.) represent these fossils of their na- 

 tural size. See description of this Plate for farther details respecting 

 them. 



