612 GEOLOGY. 



by the neuropterous group, represented by ancestral mayflies, these 

 two groups making up perhaps 90 per cent of the whole. Hemiptera 

 (bugs), which had appeared earlier, and possibly Coleoptera (beetles) 

 were present, but there is no evidence of bees or other Hymenoptera, 

 or of butterflies, moths or other Lepidoptera, and no probability of 

 their existence, since the flowering vegetation on which they are depend- 

 ent had not yet appeared. There is also no record of flies (Diptera). 

 The evolution of the class was therefore quite one-sided, and essentially 

 ortho-neuropterou's. Curious forms were developed within these 

 orders, and rather remarkable dimensions appeared in some cases, 

 spreads of wing of a foot or more being reported. The fossilization 

 was very irregular, but rather wide-spread, but the species seem to be 

 very local. This may be due to the probable fact that the different 

 localities where they have been found represent different horizons. 

 If this alternative be accepted, it probably implies a rather rapid change 

 of species, which is not improbable under the extraordinary condi- 

 tions that surrounded them. 



Spiders, scorpions, and myriopods. — As early as 1890 Scudder 

 had reported 75 species of arachnids (Fig. 284, h) and 40 species of 

 myriopods (Fig. 284, /); scorpions (Fig. 284, g) also were present. 

 Some of the myriopods were vegetable eaters, but one can only wonder 

 what air these spiders and scorpions lived on. The record probably 

 does } not tell the whole story. 



Land snails (Fig. 284, d and e), in several species, have been iden- 

 tified. ;;y 



From the foregoing it is apparent that the air-breathing com- 

 munity had become somewhat large and diverse, embracing a varied 

 group of amphibians, many insects, spiders, and myriopods, and some 

 scorpions and snails. It is obvious that all speculative assignments 

 of carbon dioxide in the atmosphere must be limited to quantities 

 compatible with this life, and the life of flying insects is of a high 

 order of activity. 

 fi^-i . r 1o , ■" 



!l] III. The Fresh-water Life. 



Besides " fresh-water plants, the life of the land waters appears 

 to have consisted of certain amphibians (and of all in their early stages), 

 of fishes, mollusks, crustaceans, probably of the larval forms of cer- 



