302 THE GEOLOGICAL RECORD [CH. 



are of this latter character, being usually impressions of wings or 

 parts of wings, very seldom of the whole insect. This fact should 

 make a classification based chiefly on the wing-venation, as in 

 the case of the Odonata, more fully appreciated. In the chain of 

 phylogenetic evidence, the value of a single impression of a com- 

 plexly-veined Odonate wing may easily outweigh that of a large 

 number of impressions from a group such as the Coleoptera. 



Fossil insect remains have been reported to occur as far back 

 as Silurian times. We are, however, on safe ground if we follow 

 Handlirsch in rejecting all those of this Age so far brought to 

 light. The Devonian strata have so far yielded none, nor have 

 the Lower' Carboniferous beds. But, m the Upper Carboniferous 

 rocks, we suddenly come upon the remains of a wild riot of teeming 

 insect life. As it first discloses itself to our view, the geological 

 record shews us the Insecta in many ways almost at the maximum 

 of their development, particularly in regard to size. Unless, 

 then, we postulate a rise of startling rapidity, we must admit 

 that our record does not reach back anywhere near the origin of 

 the Class, but rather starts near the middle, at what we may call 

 the Giant Age of Insects. Those who would study interesting 

 theories as to the origin of insects are referred to the hypotheses 

 of Lameere 1 and Handlirsch [67]. In this book, we shall give a 

 review of the various stages in the evolution of the Odonata, 

 as far as our record enables us to do so, together with a short 

 account of the conditions which probably prevailed in the four 

 great Odonate-bearing beds from which our information is chiefly 

 derived, viz. Commentry, Solenhofen, Florissant and Oeningen. 



The Palaeozoic Record. 



Our record opens, then, in the rich coal-measures of Commentry, 

 near St Etienne in France, where the labours of Brongniart[i7] and 

 Meunier[93] have exposed for us a wonderful collection of fossil 

 insects of bewildering variety. These are characterized by two 

 points the large average size of the insects, and the density 

 of their wing-reticulation. Even the Cockroaches, which are the 

 first to be recognized as approximating to a present-day type, 



1 Manuel de la faune de Belgique, Tome n, A. Lameere, Brussels, 1900. 



