26 ICHNOGRAPHS OF THE 



mals whose prototypes are to be found in the existing classes of Birds and 

 Reptiles. Impressions of Fishes also occur abundantly at Turner's Falls, in beds 

 alternating with the footprints. While, therefore, the shores of the ancient sand- 

 stone basin were thronged with air-breathing, warm-blooded animals, its waters 

 teemed with fishes and amphibious creatures. 



Next, and lastly, in this interesting drama of life we have the class Insecta ; 

 and of all the fossils in the sandstone strata there are none that excite admiration 

 and wonder so much as these delicate vestiges of insects. Their impress is 

 unblemished. The gigantic footprints confound the imagination by their immen- 

 sity; but these inimitable inscriptions interest us by their surprising delicacy and 

 beauty (Plates 40, 41, and 42). 



Associated with these attenuated footprints are the trailing impressions of 

 larvae, which are abundant in most localities. There are also other markings 

 upon the sandstone strata resulting from organization, the meaning of which is 

 incomprehensible. The fossils delineated upon Plates 43 and 44 are of this 

 description. It will require long years of patient investigation to solve the mys- 

 teries that are written in the sandstone language. Even the foiling rain has 

 registered its duration and intensity upon the impressible strata. 



It is unfortunate, for a satisfactory solution of the obscure origin of the foot- 

 prints, that the osseous systems of the animals making them cannot be recognized. 

 Bones have been occasionally found; but in a condition so imperfect as to exclude 

 legitimate conclusions. They are, however, uniformly hollow, and are fdled with 

 the same material as the rock in which they occur. That the skeleton should 

 be associated with footprints, it is indispensable that the animals should perish 

 upon the marginal grounds of the sandstone basin, which were periodical!}' sub- 

 merged, and that their bodies should be immediately buried by an overspread 

 of the materials of the succeeding stratum. But the cylindrical, permeable bones 

 of birds would cause the carcass to be lifted and floated away by the retreating 

 waters, and hence it would be deposited in places remote from the stratified 

 division of the rock. The discovery of the skeleton, therefore, cannot be confi- 

 dently expected in the fossil-bearing strata. 



Footprints in situ. — When the footprints are contemplated in their original 

 situation, their importance, as indicative of events that transpired in a remote 

 geological era, is strikingly manifest. The sandstone strata have been elevated 



