430 



MESOZOIC TIME. 



and probably also of that of Birds. Among these types, the Saurian 

 continued rapidly to rise in perfection, with the following periods of 

 the age ; while Birds and Mammals remained of inferior types, the 

 forerunners of an age of higher progress. 



While Birds were just beginnings in long-tailed or Reptilian species, 

 and Mammals in the semioviparous Marsupials, the corresponding 

 inferior division of Reptiles, the Amphibians, here passed their culmi- 

 nation, the Labyrinthodonts ending and the Amphibians being after- 

 ward fewer and smaller. 



Remarkable harmony of form characterized the higher terrestrial life. 

 The group that gathered over the mud-flats of the Connecticut com- 

 prised the biped, scale-covered, crocodile-toothed Amphibians, from 

 two or three inches to twelve or fifteen feet in height ; Dinosaurs that 

 could raise themselves erect, and march off like birds ; Birds measur- 

 ing height with the Amphibians, and outreaching them by their longer 

 necks ; and Marsupial Mammals with their hind-legs probably the 

 longer, kangaroo-like. There was throughout a great development of 

 the posterior extremities. All were oviparous vertebrates, except the 

 semi-oviparous Marsupials. 



The rocks, both in Europe and North America, were, to a large ex- 

 tent, of marsh, shallow-water, or estuary origin. But, on the borders 

 of southwestern Austria, there was an open sea, with clear waters ; 

 and extensive limestone formations were in progress, thus anticipating 

 the conditions that characterized much of Britain and Europe in the 

 era of the Lias. 



Climate. — The occurrence of the Trias in Spitzbergen, with some 

 of its characteristic fossils, is evidence of a moderate climate in the 

 Arctic. At the same time, the fact (learned from the St. Cassian 

 beds) that many Paleozoic genera continued far into the Triassic era, 

 and perhaps nearly to its close, south of the latitude of Vienna, while 

 absent from northern Europe, appears to be evidence of unlike zones 

 of temperature over that continent — a warmer southern half, and a 

 colder northern. It is not improbable that the warm seas of the In- 

 dian Ocean then swept over southern Europe. It may be that the 

 extermination of life terminating Paleozoic time — one of the most 

 universal in geological history — was due to the intervening of an era 

 of cold climate after, or cotemporaneously with, the mountain-making 

 epoch which gave the Alleghanies birth ; that the cold climatal condi- 

 tions were brought on by Arctic elevations, as well as by upward 

 movements of land in the higher temperate latitudes ; and that the 

 cold Arctic oceanic currents thus produced, to which the destructions 

 of oceanic life were owing, did not affect so seriously parts of southern 

 Europe, owing either to the lay of the emerged land, or to the Indian 



