332 /. D. Dana on American Geological History, 



a continent now sunk in the ocean. No facts prove that such a 

 continent has ever existed, and the whole system of progress, as 

 I have explained, is opposed to it. Moreover, gravel and sands 

 are never drifted away from sea-shores, except by the very 

 largest of rivers, like the Amazon ; and with these, only part of 

 the lightest or finest detritus is carried far away ; for much the 

 larger part is returned to the coast through tidal action, which 

 has a propelling movement shoreward, where there are sound- 

 ings. The existence of an Amazon on any such Atlantic con- 

 tinent in Silurian, Devonian, or Carboniferous times, is too wild 

 an hypothesis for a moment's indulgence. 



"V. The bearings of the facts in American Palaeontology on 

 the science, might well occupy another full discourse. I will 

 close with brief allusions to some points of general interest. 



1. The change in the Fauna of the globe as the Age of Man 

 approaches, is one of the most interesting facts in the earth's 

 history. It was a change not in the types of the races, (for each 

 continent retains its characteristics,) but a remarkable dwindling 

 in the size of species. In North America the Buffalo became 

 the successor to the huge Mastodon, Elephant, and the Boothe- 

 rium ; the small Beaver to the great Castoroides ; and the exist- 

 ing Carnivora are all comparatively small. 



Parallel with this fact, we find that in South America, as Dr. 

 Lund observes, where, in the last age before Man, there were 

 the giant Megatherium and Grlyptodon, and other related Eden- 

 tates, there are now the small Sloths, Armadillos, and Ant- 

 eaters. 



So, also, on the Oriental continent, the gigantic Lion, Tiger, 

 Hyena, and Elephant, and other monster quadrupeds, have now 

 their very inferior representatives. 



In New Holland, too, the land of Marsupials, there are Mar- 

 supials still, but of less magnitude. 



2. This American continent has contributed to science a 

 knowledge of some of the earliest traces of Peptides,' — the species 

 of the Pennsylvania coal formation, described by Mr. King and 

 Mr. Lea, and others from the Nova Scotia coal-fields, discovered 

 by Messrs. Dawson and Lyell. 



It has afforded the earliest traces of birds thus far deciphered 

 in geological history, — the colossal and smaller waders, whose 

 tracks cover the clayey layers and sandstone of the Jurassic 

 rocks in the Connecticut valley. The earliest Cetacea yet known 

 are from the American Cretaceous beds, as described by Dr. 

 Leidy. And among the large Mammals which had possession 

 of the renewed world after the Cretaceous life had been swept 

 away, the largest, as far as has been ascertained, lived on this 

 continent. The Palaeotheria of the Paris Basin, described by 

 Cuvier, were but half the size of the allied Titanotheria of Ne- 

 braska. 



