ON CERTAIN PORTIONS OF THE SKELETON OF PROTOS- 

 TEGA GIGAS COPE. O. P. HAY. 



The Dermochelyoid turtle, Protostega gigas, was first described 

 by Professor E. D. Cope in Proc. Amer. Phil. Soc., 1-871, page 172, 

 and again in the same publication in 1872, page 403. In 1875, m n ^ s 

 ''Cretaceous Vertebrata," pp. 99-113, pis. IX-XIII, the same writer 

 more fully described and illustrated the structure of this remarkable 

 reptile. 



The materials which were in Professor Cope's hands consisted of 

 a number of vertebrae, ten ribs, some marginal bones, certain por- 

 tions of the skull, some limb bones, and some large plates. Of the lat- 

 ter there were what the describer regarded as two entire and parts 

 of one or two others. These plates he considered as belonging to the 

 carapace, and this was supposed to be free from the ribs, as the pecu- 

 liar carapace otDermochelys is free from the ribs of that turtle. In this 

 conclusion he was undoubtedly wrong, as was later shown by Dr. G. 

 Baur (Biolog. Central blatt, vol. 9, p. 190). This author pointed out that 

 the plates were components of the plastron, an opinion that finds 

 abundant confirmation in the materials here to be described. These 

 consist of a large portion of the plastron of a large individual whose 

 remains were entombed in the Cretaceous deposits of Butte Creek, 

 Kansas. As shown in Plate IV, there are present the hyoplastron 

 and the hypoplastron of the left side almost complete. There are 

 also portions of the same bones belonging to the right side. These 

 parts of the plastron were also accompanied by the nuchal. 



The length of _the hyoplastron and the hypoplastron taken to- 

 gether amounts to 1.2 metres, including the estimated length of a 

 piece missing from near the hinder end of the hypoplastron. These 

 two bones are united by suture, which may be seen immediately in 

 front of the fracture produced in excavating the fossil. The relation 

 of these two bones is therefore unmistakably indicated. The suture 

 between the two bones is a very short one, in comparison with that 



of Thalassochelys. 



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