CURIOUS GEOLOGICAL FACTS. 451 



tially composed of Mya arenaria, with some 

 Natica heros and Purpura lapellus, all of 

 which live now upon the shore ; but we have 

 not yet been able to ascertain whether this 

 bank penetrates across the whole hill, like the 

 bank of zostera. 1 



I abstain at present from any comment on 

 these facts, and only insist upon the amazing 

 freshness and remarkable state of preserva- 

 tion of the zostera and the fossils accompany- 

 ing it. This is the more surprising, because 

 in our journey to Niagara, Mr. Desor and I 

 assured ourselves that the river deposits, in 

 which, among other things, the mastodon is 

 found with the fresh - water shells of Goat 

 Island, are posterior to the drift. It is a fact 

 worth consideration that the mastodons found 

 in Europe are buried in true tertiary forma- 

 tions, while the great mastodon of the United 

 States is certainly posterior to the drift. Shall 

 I then dare to say that the fragments of wood 

 found in the bed of zostera mentioned above 

 are artificially modeled, and that, could one 

 believe one's eyes, the traces of human in- 



1 I have satisfied myself that this bank of mya is simply 

 shored up against the slope of the hill and does not pene- 

 trate the interior of the drift more than the bank of living 

 mya on the present beach below. 



