GEOLOGY. 220 



southward of that point. These bones evidently all belonged to 

 the same individual. In each case the lower part of the pot-hole 

 was filled with gravel, on which rested a deposit of river oozo and 

 mud, in which the bones were imbedded. Upon this, in all the 

 pot-holes, was a deposit of peaty matter and mud, and in the 

 larger pot-hole were trunks of trees of several species, and in 

 great abundance. The distribution of these bones in the manner 

 described could never have taken place according to the usually 

 accepted mode of the imbedding of the animal in swamps, etc., 

 and Prof. Henry argued that they could have been thus dis- 

 posed either by the action of moving water or of ice. He was in- 

 clined to the latter view, and that the remains in question had 

 been frozen into the ancient glacier covering the country, as 

 the remains of the mammoth in Siberia ; and that, on the melting 

 of the glacier, these bones were dropped and carried into the cavi- 

 ties where they have now been found. 



Prof. Agassiz coincided with the latter supposition, but thought 

 that Prof. Hall did not go far enough in his views on the glacial 

 action. Not only was the disposition of the bones the result of 

 that action, but the pot-holes were also formed by glaciers. They 

 were caused by water- falls, as the formation of precisely similar 

 holes by these means, in Switzerland, fully demonstrated. 



Both conclusions, as to the age of the mastodon and those re- 

 lating to the glacial action in the distribution of the bones, being 

 disputed, Prof. Dawson, of Montreal, declared himself a disbe- 

 liever in the American glacial theory. Other eminent geologists 

 held the same opinion, and the mastodon was in turn referred to 

 several ages before, after, and during the glacial periods. 



If the views of Prof. Hall be accepted, it will place the age of 

 the mastodon anterior to the last glacial epocli. The remains 

 of the mammoth, or fossil elephant, occur under similar circum- 

 stances, and were no doubt coeval with the mastodon. 



SILURIAN FOSSILS. 



According to Dr. Bigsby's catalogue of Silurian fossils from all 

 parts of the world, as published in the " Proceedings of the Royal 

 Society, 11 No. 90, 1867, there are 3,145 known American species, 

 and 4,325 European, of which only 179 are common to the two re- 

 gions. In the primordial zone, the first in which a true fauna has 

 been discovered, we find evidence of the existence of more than 

 900 species. He finds that 12 per cent, of the whole number of 

 species occur in more than one horizon, and that the same species 

 may be typical of one horizon in one country, and of more than 

 one in another. Of the species which pass into the Devonian pe- 

 riod, he has identified 42, and only one of these (Ckonetes sarcinu- 

 lata) is known to have lived in the carboniferous period. These 

 extra-epochal species, as he calls them, were of migratory habits, 

 few being found in two epochs in the same country, but in differ- 

 ent countries. 



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