ANCIENT CLIMATES 481 



Now while one swallow does not make a summer, one reef -building 

 coral, or one palm, or one cyead does, since neither one of these organ- 

 isms now lives outside of a warm climate. 



Paleozoic Climate of the West Coast 



All the Paleozoic sediments on the west coast are marine, and 

 while the record is fragmentary, the evidence points uniformly to warm 

 temperature of the sea, and, thus by inference, of the land. The Lower 

 Cambrian, or Pre-Cambrian, glaciation of China and Australia has not 

 been recognized in this part of the world, but this is merely negative, 

 since land formations of that period are unknown here. 



The Lower Cambrian limestones of Inyo County, California, and 

 the adjacent region of Nevada, have extensive coral reefs of Archseocy- 

 athidas; similar reefs are known in Europe and Australia, but not in 

 the Arctic region. 



In the Silurian of Plumas County, and the Devonian of Shasta 

 County, California, there are coral reefs composed of Favositidas and 

 Tetracoralla, and in both these ages similar reefs are known in Siberia 

 and Alaska, which may show that the temperature of the sea had grown 

 warmer in the middle Paleozoic, with a northward extension of the 

 isotherms. 



The Carboniferous of Shasta and Plumas counties, California, has 

 great limestone masses full of reef-building Tetracoralla, and similar 

 reefs are known up to 82° N. lat., and down to the equator. "Whatever 

 the temperature was, it was remarkably uniform. The flora of the 

 Coal Measures 2 in the northern hemisphere indicates a warm and 

 equable climate for the land, extending up into the Arctic region, and 

 without evidence of any trace of climatic zones. 



The Permian, or Upper Carboniferous, glaciation, which was so 

 widespread in India, Australia, South Africa and South America, has 

 not been recognized in North America. But this event is now 

 recognized as the greatest catastrophe in geologic history, and its 

 effects probably extended far beyond the limits of glaciation. With 

 the accompanying lowering of oceanic temperature, near the end of the 

 Paleozoic era, the ancient types of reef-building corals, the Favositidaa 

 and Tetracoralla, disappeared. Hardly anything but solitary corals, 

 that may have been deep-water forms, are left in the Permian, and in 

 the Lower Triassic no corals of any sort are known. 



The Hexacoralla, the modern reef-builders, had already originated 

 in the Paleozoic, but were then little developed, unspecialized types. 

 They escaped the general catastrophe either by being distributed in 

 regions where the destruction did not take place, or by being then deep- 



2 David White, Jour. Geol, Vol. XVII., No. 4 (1909), p. 338. 

 vol. lxxvi.— 33. 



