AUTHOR'S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, MAT 22 



ON THE PHYLOGENY OF THE SHELL OF THE 



TESTUDINATA AND THE RELATIONSHIPS 



OF DERMOCHELYS 



OLIVER P. HAY 



Associate of the Carnegie Institution of Washington 



ONE TEXT FIGURE AND TWO PLATES 



Some years ago the testudinate genus Dermochelys was an 

 object of interest to the writer, and he discussed the structure 

 and origin of its pecuhar shell and the systematic position of the 

 animal (Amer. NaturaHst, vol. 32, 1898, pp. 929-948. The 

 Fossil Turtles of North America, 1908, p. 23). Since that time 

 several important papers on the subject have been published, 

 especially by Dr. J. Versluys and his students. The writer 

 wishes to take up again briefly the subject. Inasmuch as Doc- 

 tor Versluys' paper, "tJber die Phylogenie des Panzers der 

 Schildkroten und iiber die Verwandtschaft der Lederschild- 

 krote Dermochelys coriacea" (Palaeont, Zeitschr, Bd. 1, 1914, 

 S. 321-347), furnishes a resume of the results obtained by him- 

 self and his coworkers, this paper onlj^ will be directly considered. 



Doctor Versluys rightly emphasizes the importance of Dermo- 

 chelys, recognizing that either it represents a very old lateral 

 branch of the testudinate stem or that in its shell it presents a 

 remarkable example of a rapidly divergent development. He 

 concludes that the view has been confirmed which makes of 

 Dermochelys a not very distant relative of the Cheloniidae. 



Dermochelys is regarded by Doctor Versluys as belonging to 

 the Cryptodira for two principal reasons. The first is that the 

 neck is bent in a vertical plane, as in the Cryptodira, instead of 

 a horizontal one, as in the Pleurodira; the second, that the indi- 

 vidual vertebrae conform in the shapes of their articular ends to 

 the arrangement in the Cryptodira. As to the first proposition 



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