﻿OF THE VALLEY OF THE CONNECTICUT. 215 



lar, but imperfect impression, showing neither phalangeal ranks or nails. It has the 

 fourth toe pointing backward, as in many orders of existing birds. The rolling up of the 

 mud anterior to the lateral toes, and a prolonged depression posterior to the heel, sug- 

 gests the idea of the slipping of the foot, which often happens. The clearness and sym- 

 metry of the impress renders it very elegant ; still it is but an outline impression. 



Fig. 3 is a beautiful example of footprints, perfectly developed in all respects. The 

 order of articulations, and the imprint of the tarsus and nails, are clear and unequivocal. 

 This variety is common at Turner's Falls, but is seen at no other locality. It is shown 

 in consecutive series upon Plate I., which contains several examples. The line of fifteen 

 impressions, running upward through the whole length of the plate, belongs to this spe- 

 cies. That running transversely across the upper half from left to right is another ; and 

 there is still another at the bottom of the plate, crossing from right to left. The impress 

 is usually superficial, but always accurate. The position of the footprints a and b would 

 seem to be irregular, but it must be remarked that the feet of birds almost invariably 

 point inward. In reptilian quadrupeds the reverse happens, their feet uniformly pointing 

 outward ; and this is an important distinction in studying these fossils. The central toe in 

 birds usually points to the succeeding footstep. The direction, therefore, in which Fig. 3 

 moves is not perpendicular to the plate, but obliquely to the right. To know where 

 the repetition of a will happen, take the distance a and b, and the direction of the cen- 

 tral toe b, and the proper place will be accurately given. The original slab of Plate I. 

 was incrusted by a thin layer of micaceous sandstone, the removal of which required 

 the laborious application of the chisel ; yet so accurate was the principle, that I uncover- 

 ed row after row, cutting down at once upon the footsteps only. A line, therefore, con- 

 necting these impressions runs alternately from side to side, and its obliquity depends 

 upon the length of the leg. Thus, in Fig. 3, the zigzag direction of this line is consider- 

 able, as will be seen by reference to Plate I., while the impressions in Plate II. are almost 

 in a direct line. 



The distinctive features of this species, then, consist in the strongly marked and taper- 

 ing toes, long and blunt nails, the divergence of the lateral toes, and the broad space which 

 separates them from the central one and the tarsus, which is separated from the toes, and 

 is placed farther backward than usual. The lateral toes with the double-headed tarsus 

 represent the letter V correctly. 



Fig. 4 is a beautiful footprint, and is the type of a series of impressions to which I 

 shall bespeak particular attention. It belongs to that group represented by Plate II. 

 Its peculiarity consists in its massive toes, its long and narrow impression, its graceful 

 outline, the perfect impression of the tarsus and nails, and its great length of stride. The 



