16 Secondary Fossils. 



turn alternately right and left. In one slab found at Turner's 

 Falls on the Connecticut by Dr Deane, the fine matrix has 

 retained marks of the integument or skin of the foot. This 

 specimen is now in the museum of Dr Mantell, and the im- 

 pression was recognized by Professor Owen as resembling 

 the skin of an ostrich and not that of a reptile. Such a test, 

 in addition to the other evidence before mentioned, should, I 

 think, remove all scepticism in regard to the ornithic nature 

 of most of these bipeds. The size indeed of some of the fossil 

 impressions seemed at first to raise an objection against their 

 having belonged to birds, as it far exceeded that of any living 

 ostrich, but the Dinornis and other feathered giants of New 

 Zealand have removed this difficulty. The foot-prints are 

 accompanied by numerous coprolites, and Mr Dana has de- 

 rived an ingenious argument from the analysis of these bodies, 

 the proportion they contain of uric acid, phosphate of lime, 

 carbonate of lime, and organic matter, shewing that, like 

 guano, they are the droppings of birds rather than of reptiles.* 

 Still, it is asked, whether, if birds were so abundant, we ought 

 not to meet with some of their bones in a fossil state, — a 

 remark, be it observed, which is equally applicable to the 

 associated quadrupedal imprints. In reference to this ques- 

 tion, I took pains, when on the shores of the Bay of Fundy 

 after I had examined the red sandstone of the Connecticut, 

 to inquire whether, in digging trenches through the red mud 

 of recent origin, from which the tide has been excluded by sea- 

 banks, they had ever found the bones of birds, and I could hear 

 of no instance, although I saw the sandpiper, or Tringa minuta, 

 making every day those lines of impressions in the mud bor- 

 dering the estuary which I have described and figured in my 

 " Travels." My friend Dr Webster, of Kentville, Nova Scotia, 

 has recently sent me some fine examples of rain-drops, which 

 he saw formed during a shower on this modern mud, and casts 

 of which project in relief from the under- side of an incumbent 

 layer of the same argillaceous deposit, thrown down during 

 a subsequent rise of the tides. Thus marked and traversed 

 by cracks caused by shrinkage, and containing the foot-prints 



* Amer. Jour, of Science, vol. xlviii., p. 46. 



