20 ICHNOGRAPHS OF THE 



prints and bones from the New Red Sandstone of Pennsylvania (Proc. Am. Phil. 

 Soc. 1849) ; and by Charles Lyell, Esq., upon Footprints of Birds and Impressions 

 of Rain-drops in the Valley of the Connecticut River, communicated to the London 

 Geological Society. 



The descriptive papers hitherto published by the author have been contributed 

 to various numbers of Silliman's Journal; to the Journals of the Society of Nat- 

 ural History, Boston ; the Academy of Natural Sciences, Philadelphia ; and to the 

 Academy of Arts and Sciences, Boston. 



This list, so far as I am able to ascertain, includes the principal contributors 

 to the literature of the sandstone footprints of this country. It is also proper 

 to allude to the successful labors of those gentlemen who have quietly pursued 

 their investigations in the field without recording the results of their obser- 

 vations. Among the most conspicuous was the late Mr. Marsh of Greenfield, 

 who accumulated a series of footprints of great value to science. Roswell Field, 

 Esq., a gentleman of acute powers of observation, succeeded Mr. Marsh as an 

 explorer; and, possessing an intimate knowledge of the subject, began at once 

 to make discoveries of significant importance. His estate, being at Turner's Falls, 

 embraces the richest localities yet discovered, and his success has been very remark- 

 able. In the preparation of this paper the author will have frequent occasions 

 to acknowledge his obligations to him for original materials and observations. 



Analogies of the Footprints. — It is proper, for a clear comprehension of this 

 topic, to premise, that the footprints will be assumed to indicate animals whose 

 representatives .are included in the existing classes of Birds, Reptiles, and Insects ; 

 and there are also presumptive proofs that the Mammalian class also coexisted. 

 The birds may, with probability, be subdivided into two principal orders, — the 

 waders proper, and the brevipennate or struthious tribes. They were usually 

 tridactylous, but a portion of them possessed a fourth or rudimentary toe, that 

 performed no part in the office of walking. Without exception there are three 

 toes pointing forward, and there are never more than four toes. Each of these 

 divisions of the omithoid footprints included a great variety and combination of 

 forms, some of which continued to be produced throughout the entire deposition 

 of the sandstone rock, while others successively disappeared and were replaced 

 by new and distinct creations. 



The reptilian footprints, although numerous, bear but a small proportion to 



