﻿218 ILLUSTRATIONS OF FOSSIL FOOTPRINTS 



Fig. 1, the clay upon which the bird trod was yielding, yet not too soft to retain the form 

 of the foot perfectly. The tarsus, phalanges, and nails are distinct. In Fig. 2, the impress 

 is flattened by the resistance of the stratum to the weight of the bird ; still, the articula- 

 tions are distinct. The stratum is covered with the marks of rain-drops, but the weight 

 of the bird obliterated them completely. I have often seen, in long rows of footprints, 

 the phenomena presented by these two figures. The first impressions of the series would 

 be flattened, the succeeding ones deeper, and vice versa, the animal passing from one con- 

 dition of the strata to the other, or from the higher parts of the shore into the water, or in 

 the opposite direction. Fig. 2 is spread more than Fig. 1 ; but the difference is attribu- 

 table to the different degrees of solidification of the strata. The most elegant examples 

 of footprints are often those which are completely flattened, for they usually present a 

 clearer definition than those which are deep. 



Plate VI. 



The figure represented by this drawing is the middle toe of a footprint, fifteen inches 

 in length, and ten in breadth between the extremities of the lateral toes. The stupen- 

 dous magnitude of the extinct birds, as indicated by this fine impression, is without parallel 

 in existing types. The area of the foot is at least four times greater than that of any 

 living bird, and doubtless the true proportions were still more extraordinary. Colossal 

 birds abounded in vast numbers during the sandstone era, for their vestiges are distrib- 

 uted over the entire extent of the sandstone basin. They are most numerous at Tur- 

 ner's and at South Hadley Falls. 



The phalangeal divisions of this immense footprint are perfectly defined ; and between 

 it and Fig. 1, Plate III., there occurs, in the ornithic footprints of Connecticut River, a 

 regular gradation of intermediate forms. I obtained this footprint from Turner's Falls. 



Plate VII. 



Aside from its vast size, this is a beautiful and exceedingly interesting footprint, on 

 account of the distinct impression of the heel, phalanges, and nails. The figure is taken 

 from the specimen of Mr. Marsh, which is represented on Plate II. It holds an interme- 

 diate grade between the figures of Plates V. and VI. ; and they were all, in my opinion, 

 impressed by different individuals of the same species of bird, in various stages of growth. 

 The remarks upon Figs. 3 and 4, Plate IV., are applicable in this instance. 



Plate VIII. 

 The footprints upon this plate embrace three distinct species of quadrupeds from the 



