JURA-TRIAS IN AMERICA. 453 



the greatest perfection, viz., ripple-marks, rain-prints, sun-cracks, leaf- 

 impressions,and tracks of animals. It is evident, therefore, that this 

 was, throughout, a littoral or slioal-icater deposit. But it is at least 

 5,000 feet thick. Therefore, there must have been subsidence to that 

 extent. Here, then, we have evidence of rapid deposit (for the mate- 

 rials are coarse), invasion of interior heat with aqueo-igneous fusion, 

 subsidence, formation oi fissures, and ejection of lava. 



These sandstones are poor in fossils, but the few that are known in- 

 dicate the horizon of the Keuper or Upper Triassic of Europe. As 

 these are found near the middle of the series, it is probable that the 

 series represents the whole of the Trias and part of the Juras of Europe. 



The Record. — The general redness of the sandstone is sufficient evi- 

 dence that organic remains are very scarce ; and so, indeed, we find it. 



Fig. 714.— a, Frond; b, Cone (after Hitchcock). 



Two or three fishes, a few leaves, the most perfect of which is a species 

 of fern — Clathopteris — and a fir-cone (Fig. 714), and a few small frag- 

 ments of thin, hollow bones, which may have belonged to either birds 

 or reptiles, are all that have been -yet found. 



But by far the most interesting portion of the record in this locality 

 consists of tracks. These are partly tracks of Insects and Crustaceans, 





.^r- ^\\ ^ > — — ' — -v Fig. 716.— Larva of an 



^->-^^o^-— _— ^ ^\ v *~ ^ ^-- ~- ., ^^^-^^sO*- Ephemera (after Eitch- 



v>^-v^.^>-^-~~"^ <v - s v.^.« — •— *^^ cock). 



Fig. 715. — a, b, c, Tracks of Insects, Crustacea, or Worms (after 

 Hitchcock). 



and partly of Reptiles and, possibly, of Birds. Some of those which 

 have been referred to Crustaceans and Insects are shown in Eig. 715, 



