CONNECTICUT RIVER SANDSTONE. 53 



footprints, the position of the posterior foot is in uniform correspondence with 

 that of a bird, while at the same time it is attended by its companion, as repre- 

 sented by the Plates. 



These singular impressions, like those upon Plates 31 and 32, are entitled 

 to particular consideration, inasmuch as they suggest doubts as to an ornithic 

 origin of the bipedal footprints. The posterior trifid feet are just as susceptible 

 of comparison with the feet of living birds, as those bipedal impressions that 

 have been with great reason supposed to belong to birds; but, being associated 

 with other impressions of reptilian character, it is certain that the animal could 

 have no affinities with birds, but belonged to a distinct race. 



It is difficult to avoid the presumption that the footprints upon Plates 31, 

 32, 33, and 34 were impressed by animals that were identical, except so far as 

 they were distinguished by specific difference, and that they could jump like the 

 kangaroo, or walk as quadrupeds, and, perhaps, as bipeds. If the creatures impress- 

 ing Plates 33 and 34 could move by leaping, they would produce the same series 

 of impressions as upon Plates 31 and 32; and if, on the other hand, the order 

 be reversed, the latter walking as quadrupeds, the impressions would be identical 

 with those of Plates 33 and 34; and there can be no question that, if any of 

 these creatures walked erect, they would produce impressions in no way different 

 from those supposed to be due to birds. From the intimate relations of the 

 two sets of impressions, it is reasonable to suppose that their authors possessed 

 common attributes, and could either walk or jump at pleasure. 



If it could be further proved that these animals possessed the power of 

 walking upon their posterior feet alone, the question of the ornithic origin of the 

 sandstone footprints would be definitely settled. If the posterior feet of Plates 

 33 and 34 were disconnected from their associated reptilian impressions, they 

 would at once, upon the rules of comparison, be pronounced to be ornithic. 

 Prior to the discovery of the ornithic-reptilian impressions, no fact has ever 

 occurred to disturb the theory of the ornithic character of the tridactylous foot- 

 prints, for the grounds upon which this belief rested seemed impregnable. But 

 a combination of ornithoid and reptilian footprints proves that a portion of the 

 sandstone animals, having ornithic feet, can have no relation to birds; and this 

 fact raises a strong presumption, that the other portion may yet, by future dis- 

 covery, be determined to belong to quadrupeds. 



There is an incidental circumstance, entitled to some consideration in deter- 



