OF THE VALLEY OF THE CONNECTICUT. 
211 
here, only, that the fossil skeleton will be found. Such a discovery would supply the 
legitimate elements of specific distinctions. Nevertheless, we can unquestionably deter¬ 
mine the classes to which the authors of the footprints belonged by the principles of re¬ 
ciprocal relation. The foot of a tridactylous bird has three phalangeal bones for the inner 
toe, four for the middle, and five for the outer ones; but the impression of the terminal 
joint is that of the nail only. Consequently, the inner toe has two, the middle three, 
and the outer four distinct lobate expansions, corresponding to the respective joints. Now, 
it is this immutable law that connects the extinct with living birds. That such impres- 
t # # ^ Til 
sions are due to birds is proved by a principle nearly as infallible as that supplied by 
osseous structure. Taken in connection with the accompanying phenomena, such as the 
alternation of the feet, and the impression of the ungual and tegumentary tissues, in 
both living and fossil races, the grounds of analogy are simple and unimpeachable. 
The ancient birds were mostly tridactylous; many, however, have a fourth toe point¬ 
ing backward. Some were no larger than small living birds; but in general, the impres¬ 
sions indicate animals vastly larger than their living representatives. Quadrupeds co¬ 
existed with the birds, and their impressions often occur upon the same stratum. These 
animals were diminutive, and doubtless belonged to several families of Batrachian 
reptiles. 
The country of the extinct animals was extensive. Commencing near the northern 
boundary of Massachusetts, it stretches away southerly through the State into Connect¬ 
icut, and reappears in New Jersey and in Pennsylvania. But the ancient sandstone 
basin is of limited breadth in all places. It is bounded upon either hand by primitive 
formations, and through the western margins of the sandstone beds a basaltic dyke has 
been ejected, the protrusion of which has disturbed the position of the sedimentary beds, 
and afforded the opportunity to investigate their contents. The localities where foot¬ 
prints have been observed are very numerous. In general, they are abundantly found 
wherever extensive explorations have been conducted in the stratified portion of the 
sandstone. The localities that furnish the most numerous, and beyond all comparison 
the most beautiful specimens, are those at Turner’s Falls, the northern terminus of the 
sandstone beds. The models for the plates are derived from this source; whence I 
have obtained slabs containing as many as seventy-five impressions. 
With these preliminary remarks, I proceed to illustrate these footprints by presenting 
copies, selected from the most perfect and beautiful examples. The drawings were put 
upon the stone by myself, with the utmost care, and I have attempted to compensate for 
the lack of artistic execution by producing faithful transcripts of the originals. I hope 
that my efforts in this difficult undertaking may not prove entirely unacceptable. 
