348 FOSSIL FOOTPKINTS IN THE [Cn. XXII'. 



other feathered giants of New Zealand were discovered. Their dimen- 

 sions 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 origi- 

 nally trodden upon. In order, therefore, to guard against exaggeration, 

 the casts rather than the mould are relied on. These casts snow 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 JEpiornis, which has proba- 

 bly 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 

 Apterix, Professor Owen does not believe thai the vEpiomis exceeded, if 

 indeed it equalled, the Dinornis in stature. 



Among the supposed bipedal tracks, a single distinct example 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 precisely 

 on the 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 re- 

 marked that certain species of frogs and lizards in Australia 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 bipedal 

 reptile approaching the bird so nearly in the structure and shape of its 

 wing-bones and tibise, 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 num- 

 ber of the American impressions 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 re- 

 ferring 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 j^roportion they contain of uric acid, phosphate of 

 lime, carbonate of lime, and organic matter, to show that, like guano, 

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



Some of the quadrupedal footprints which accompany those of birds 

 are analogous to European Cheirotheria, and with a similar disproportion 

 between the hind and fore feet. Others resemble that remarkable rep- 

 tile, the Rhyncosaurus of the English Trias, a creature having some 



