Ch. XXII.] FOSSIL FOOTPRINTS.. 455 



The size of several of the fossil impressions of the Connecticut red 

 sandstone so far exceeds that of any living ostrich, that naturalists at 

 first were extremely adverse to the opinion of their having been made 

 by birds, until the bones and almost entire skeleton of the Dinornis 

 and of other feathered giants of New Zealand were discovered. 

 Their dimensions have at least destroyed the force of this particular 

 objection. The magnitude of the impressions of the feet of a heavy 

 animal, which has walked on soft mud, increases for some distance 

 below the surface originally trodden upon. In order, therefore, to 

 guard against exaggeration, the casts rather than the mould are relied 

 on. These casts show that some of the fossil bipeds had feet four 

 times as large as the ostrich, but not perhaps much larger than the 

 Dinornis. 



The eggs of another gigantic bird, called uffipiomis, which has 

 probably been exterminated by man, have recently been discovered 

 in an alluvial deposit in Madagascar. The egg has six times the 

 capacity of that of the ostrich ; but, judging from the large size of 

 the egg of the Apteryx, Professor Owen does not believe that the 

 uffipiornis exceeded, if indeed it equalled, the Dinornis in stature. 



Among the supposed bipedal tracks, a single distinct animal only has 

 been observed of feet in which there are four toes directed forwards. 

 In this case a series of four footprints is seen, each 22 inches long and 

 12 wide, with joints much resembling those in the toes of birds. Pro- 

 fessor Agassiz has suggested that it might have belonged to a gigantic 

 bipedal batrachian. Other naturalists have called our attention to the 

 fact, that some quadrupeds, when walking, place the hind foot so pre- 

 cisely on the same spot just quitted by the fore foot, as to produce a 

 single line of imprints, like those of a biped ; and Mr. Waterhouse 

 Hawkins has remarked that certain species of frogs and lizards in Aus- 

 tralia have the two outer toes so slightly developed and so much raised 

 that they might leave tridactylous footprints on mud and sand. 

 Another osteologist, Dr. Leidy, in the United States, observed to me 

 that the pterodactyl was a biped reptile approaching the bird so nearly 

 in the structure and shape of its wing-bones and tibiae, that some of 

 these last, obtained from the Chalk and Wealden in England, had been 

 mistaken by the highest authorities for true birds' bones. May not 

 the foot, therefore, of a pterodactyl have equally resembled that of a 

 bird ? Be this as it may, the greater number of the American impres- 

 sions agree so precisely in form and size with the footmarks of known 

 living birds, especially with those of waders, that we shall act most in 

 accordance with known analogies by referring most of them at present 

 to feathered, rather than to featherless bipeds. 



No bones have as yet been met with, whether of pterodactyl or bird, 

 in the rocks of the Connecticut, but there are numerous coprolites ; 

 and an ingenious argument has been derived by Dr. Dana from the 

 analysis of these bodies, and the proportion they contain of uric acid, 

 phosphate of lime, carbonate of lime, and organic matter, to show 



