1877.] Concerning Foot-Prints. 415 
The foot-prints found so abundantly in the Connecticut valley 
frequently seem to have been impressed upon a layer of soft mud, 
now shale, and to have been covered with a layer of sand, now 
hardened into a firm sandstone, which, upon being raised from its 
native bed, retains upon its under surface, standing out in relief, 
an exact cast of the foot-prints. These natural casts are often 
as perfect as if molded in plaster, and sometimes retain even 
the lines and creases of the skin which covered the feet of the 
animals that impressed them. These tracks have not been 
found in a few rare instances, but number many thousands, ob- 
tained from nearly forty localities in the valley of the Connecti- 
cut; the writer has also obtained several species from Pompton 
and Plainfield, N. J. 
We commonly hear these fossil foot-prints spoken of as “ bird 
tracks ;” they include, however, very many that are clearly rep- 
tilian in their character. Others have been referred to marsupial 
animals by Professor Hitchcock, to whose splendid report on the 
Ichnology of Massachusetts we would refer our readers for de- 
tailed and accurate information on this subject. 
No skeletons of these ancient inhabitants of Connecticut and 
New Jersey have been found sufficiently well preserved to sub- 
stantiate the conclusion of geologists that many of the tracks 
were made by birds, as the class is at present defined. Some 
persons are inclined to ascribe the bird tracks to kangaroo-like 
reptiles, which walked on two legs, like the gigantic Hadrosaurus 
that inhabited the shores of New J ersey in the next succeeding 
age, — the Cretaceous. Some fortunate discovery of the skele- 
tons of these animals will possibly show that they possessed some- 
thing of that strange “synthetic structure” so often met with 
geological history. It is not improbable that these earliest of 
birds possessed a combination of reptilian and avian characters, 
exemplified by the Archæopteryz,! the Pterodactyls,2 and the 
_ toothed birds from the Cretaceous formations of Nebraska. 
The principal reasons that have led geologists to consider many 
of the Connecticut foot-prints as having been made by birds are 
that the animals were clearly. bipeds, and left a tridactylous, or 
aree-toed, impression on the mud; some of them had a fourth 
1A fossil bird found at Solenhofen, Bavaria, having short, rounded wings with 
- claws attached, and a long lizard-like tail, composed of about twenty vertebræ, each 
Supporting a pair of quill-feathers. 
genus of flying reptiles belonging to the Jurassic and Cretaceous ages, which 
= membraneous, bat-like wings, that sometimes measured twenty-five feet 
ftom tip to tip. 
