INTRODUCTION, 



The remains of Birds are among the rarest of fossils, and very few 

 have been discovered except in the more recent formations. According to 

 present evidence, the oldest known Birds were imbedded in the Jurassic 

 deposits of Europe, which have yielded three individuals belonging to the 

 genus Archsopteryx, so well preserved that the more important characters 

 can be determined. The only other remains of birds found in the Mesozoic 

 of the Old World are a few specimens from the Cretaceous of England, 

 which are too fragmentary to throw much light on the extinct forms 

 they represent. 



The earliest traces of Birds hitherto found in the strata of this country 

 are from the Cretaceous, although we may confidently predict their 

 discovery in the Jurassic beds, if not at a still lower horizon. There is at 

 present no evidence whatever that any of the three-toed impressions in the 

 Triassic, described as the footprints of Birds, were made by Birds ; and 

 the proof now seems conclusive that nearly all of them are the tracks of 

 Dinosaurian reptiles, bones of which occur in the same deposits. 



In the Cretaceous beds of the Atlantic Coast, and especially in the 

 green-sand region of New Jersey, various remains of Birds have been 

 found, and described by the writer. 1 These fossils, although often in 

 excellent preservation, occur mainly as isolated bones, and hence their near 

 affinities have not as yet been determined with certainty. 



1 See Synopsis at the end of this volume. 

 1 1 



