692 GEOLOGY 



seem to have been a fitting preparation for life in the second. Yet, 

 in spite of this fact, there was a great break in the succession of 

 land life, so far as the known record shows. What became of the 

 Permian vertebrate faunas of North America is unknown, for be- 

 tween the horizons yielding Permian fossils of land animals, and 

 those yielding corresponding Upper Triassic fossils, there are 

 great thicknesses of red sandstone barren of fossils of all sorts, so 

 far as now known, and the Upper Triassic (Keuper) fauna does 

 not appear to have descended from the Permian. In Africa there 

 appears to have been a much less serious break between the land 

 life of the Permian and that of the Trias. In other continents few 

 fossils of land life of the early types have been found, and the 

 record of the Middle Trias is but little less meager. Of the life of 

 the Upper Trias the record is much fuller. The period was one of 

 great transitions, in which many types were initiated, while only 

 a few were carried to their maximum development. 



There is abundant proof of the intermingling of European and 

 American land faunas late in the Triassic period, for at this time 

 there were, in North America, representatives of groups that had 

 lived in Europe since the early Permian, but which had never 

 before appeared in our continent, so far as now known. 



The amphibians had lost the foremost place they held in the 

 Permian, though still numerous (but not in North America in the 

 early part of the period). Before its close, however, they entered 

 upon a rapid decline, from which they never recovered. Ancestors 

 of the whole tribe of terrestrial vertebrates, they soon became its 

 most insignificant representatives. 



The strange ancestral reptiles evolved rapidly. The branch 

 with the mammalian strain (p. 672, Fig. 470) seems to have been 

 left far behind by the more distinctively reptilian branch, which 

 developed greatly in the closing stages of the period when the dry- 

 ness was ameliorated and vegetation began again to flourish. Be- 

 fore the close of the period, every important group of the class had 

 its representatives. The crocodilians, the flying sauri.-ms, and the 

 scaled reptiles (lizards, snakes, etc.) came in near the close of the 

 period, as some of the older types were disappearing. 



A foremost feature of the life was the advent and rapid evolu- 



