of them was, however, published in the Proceedings of the Academy for the same year, page 234.
Additional material was shortly afterwards sent to the writer, and the important contributions on the Batrachia of the coal measures, and on the Elasmosauridæ, 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 Reptilia, the following general conclusions 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 Reptilia 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.
I 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. R. 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 Mosasauroid 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 platyurus, and its shipment in unusually good condition. Dr. E. R. 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. Lockwood, of Keyport, New Jersey, and to other friends.
