76 Fossil Footma?~ks of Turner's Falls. 



row dimensions. Numerous as they are, there is yet no confusion, 

 the successive footsteps of each row bearing a just relation to each 

 other. There appear to be three principal varieties, or perhaps 

 sizes of impressions, each of which is accurately illustrated by the 

 drawings, which were taken by my own hand. It is not however 

 strictly easy to decide that these are after all distinct varieties, 

 for setting aside the difference in size, there is great resemblance 

 in them, yet in other respects they appear to be distinct, as is in- 

 dicated by the relative length of stride and some other peculiari- 

 ties. The large foot, which has received the name of Ornithich- 

 nites Fidicoides, (Trans. Assoc. Am. Geol. Yol. T, p. 258,) has an 

 average length of stride of rather more than twelve inches, while 

 the middle size, one fourth as large, has a stride of twenty to 

 twenty three inches ! It will also be seen from the plate that 

 the zigzag direction of the steps of the O. Fidicoides, indicates 

 a heavy short-legged bird, the centre of gravity falling far within 

 the inner toe, while this line passes through or very near the cen- 

 tre of the other. This therefore seems to point out that the bird 

 must have had relatively very long legs, unless we suppose, what 

 is quite possible, that this was the running gait of a young bird. 

 The small track is very beautiful ; it is feebly impressed, from 

 which we may infer that it was a light bird, yet in the anatomy 

 of the feet and the great distance these organs are separated, it 

 bears a strong affinity to the O. Fidicoides. Whether these birds 

 were or were not distinct species, they were nevertheless grega- 

 rious in their nature, as is shown by the fact that they traversed 

 the region together, and if we separate them into generic classes, 

 it must be upon the nicest discrimination, although the structure 

 of the foot is so beautifully cast. 



The impression of a medallion is not more sharp and clear than 

 are most of these imprints, and it may be proper to observe that 

 this remarkable preservation may be ascribed to the circumstance 

 that the entire surface of the stratum was incrusted with a layer 

 of micaceous sandstone, adhering so firmly that it would not 

 cleave off, thereby requiring the laborious and skillful application 

 of the chisel. The appearance of this shining layer, which is of 

 a gray color, while the fossil slab is a dark red, seems to carry 

 the probability that it was washed or blown over the latter while 

 in a state of loose sand, thus filling up the footprints and rain-drops, 

 and preserving them unchanged until the present day — unchanged 



