2 THE EXTINCT BATRACHIA, REPTILIA 



of them was, however, piiblished in the Proceedings of the Academy for the same year, 

 page 234. 



Additional material was shortly afterwards sent to the writer, and the important con- 

 tributions on the Batrachia of the coal measures, and on the Elasmosaurida?, written. 

 The Palaeophis and some of the Testudinata and Pythonomorpha were also added. 



In the course of these investigations, prosecuted during the past six years, with 

 reference to the structure and relations of the extinct Peptilia, the following general con- 

 clusions have been attained to, besides many of lesser significance. 



First : That the Dinosauria present a graduated series of approximations to the birds, 

 and possess some peculiarities in common with that class, standing between it and the 

 Crocodilia. 



Second : That serpents exist in the Eocene formations of this Country. 



Third : That the Chelydra type was greatly developed during the American Cretaceous, 

 and that all the supposed marine turtles described from it, are really of the first named 

 group. 



Fourth : That the Peptilia of the American Triassic are of the Belodon type. 



Fifth : The discovery of the characters of the order Pythonomorpha. 



Sixth The development of the characters of numerous members of the Batrachian 

 Sub-order Microsauria in the United States. 



1 must express my obligations to Prof. Geo. H. Cook, of the Geological Survey of 

 New Jersey, who kindly placed the specimens procured during the Survey at my disposal. 

 I am also particularly indebted to Prof. John S. Newberry, of Columbia College, New 

 York, and director of the Geological Survey of Ohio, for the loan of the unique and 

 important material from the carboniferous beds at Linton, Ohio, contained in his private 

 collection. I am under similar obligations to Wm. P. Webb, Superintendent of the Land 

 Office at Topeka, Kansas, for the important type specimens of Polycotylus latipinnis, 

 and to Prof. Agassiz, for the freedom of study and description of the unequalled Mosa- 

 sauroid material in the Museum of Comparative Zoology, Cambridge. Also to Philip P. 

 Tyson, of Baltimore, for similar advantages, and to Dr. Theophilus M. Turner, of Fort 

 Wallace, Kansas, for the discovery of that extraordinary reptile, the Elasmosarus pla- 

 tyurus, and its shipment in unusually good condition. Dr. E. P. Showalter. of Uniontown, 

 Alabama, has placed me under obligation, in sending the beautiful fossil of Clidastes 

 propython. I must also express obligations to Prof Marsh, of Yale College, Dr. Lock- 

 wood, of Keyport, New Jersey, and to other friends. 



