Foot-prints. 16 



ments of drift-wood, that these beds had been formed precisely 

 under circumstances most favourable for the reception of im- 

 pressions of the feet of animals, walking between high and 

 low water. In the prolongation of the same beds in the 

 valley of the Connecticut, there have been found, according 

 to Professor Hitchcock, the foot-prints of no less than thirty- 

 two species of bipeds, and twelve of quadrupeds. Thirty of 

 these are referred to birds, four to lizards ; two are believed 

 to be those of chelonians, and six to be batrachians, the re- 

 maining two being doubtful. They have been observed in 

 more than twenty localities, which are scattered over an 

 area of nearly eighty miles from north to south in the states 

 of Massachusetts and Connecticut. After visiting several of 

 these places, I entertained no doubt that the sand and mud 

 were deposited on an area which was slowly subsiding all the 

 while, so that at some points a thickness of more than 1000 

 feet of superimposed strata had accumulated in very shallow 

 water, the foot-prints being repeated at various intervals on 

 the surface of the mud throughout the entire series of super- 

 imposed beds. When I first examined this region in 1842, 

 Professor Hitchcock had already seen 2000 impressions, each 

 of them indented on the upper sides of layers of shale, while 

 the casts of the same, standing out in relief, always protruded 

 from the lower surface of the incumbent strata. Had they 

 been concretions, as some geologists at first contended, they 

 would have been occasionally found projecting from the upper 

 sides of strata of sandstone. I was also much struck when 

 following each single line of foot-marks, to find how uniform 

 they were in size, and how nearly equidistant from each other, 

 whereas on turning to a larger or smaller set of impressions, 

 the distance separating any two tracts in the same series 

 immediately increased or diminished, there being an obvious 

 proportion between the length of the stride and the dimen- 

 sions of the creature which walked over the mud. There 

 are also a great number of examples where the trifid impres- 

 sions exhibit three marks of phalangeal bones for the inner 

 toe, four for the middle, and five for the outer one, as in the 

 feet of living tridactylous birds, and in each continuous line 

 of steps the three-jointed and five-jointed toes are seen to 



