494 



GEOLOGY 



gymnosperms ; but on this point there is not as yet complete unanimity 

 of opinion. In numbers, the ferns or fern-like forms appear to have 

 surpassed all others. 



The forest element was chiefly due to the calamites, gigantic ances- 

 tors of the horsetails, to the lepidodendrons, gigantic ancestors of 

 the club-mosses, and to the cordaites, an extinct group of gymno- 

 spermous type. All of these trees were so much better developed 

 in the Coal flora, where they reached their climax, that their discussion 

 may advantageously be deferred. 



There were not a few forms whose relations have not been made 

 out satisfactorily from the imperfect material. Among them are 

 those known as psilophyton and ptilophyton. 



The insects. — The air was partially peopled by insects at this time. 

 Numerous wings and other fragments have been found, chiefly near 

 St. Johns, New Brunswick, and these have been described and inter- 

 preted by Scudder. 1 The relics indicate that the insects were of archaic 

 and synthetic types most nearly allied to modern neuropters and 

 orthopters, but they combined characters now found in different orders. 

 The representatives of neuropterous aspect seem to have been related 

 to the mayflies (Ephemera), whose lives are spent chiefly in water, 



Fig. 226. — Platephemera antiqua, Sc. 

 St. Johns, N. B. (After Scudder.) 



Fig. 227. — Xenoneura antiquorum, Sc. From 

 St. Johns, N. B. (After Scudder.) 



the winged condition being assumed for a short period only. If this 

 were true of the ancient forms, they should be regarded as aquatic 

 rather than as aerial denizens, and scarcely as terrestrial at all. But 

 the imperfect relics perhaps do not warrant pursuing these consider- 

 ations. Fig. 226 shows the wing structure of Platephemera antiqua, 

 a large species with a spread of wing of perhaps five inches. That 



1 A list is given in Bull. No. 71, U. S. Geol. Surv., 1891. Question has been raised 

 as to the Devonian age of these. 



