280 MEMOIRS OF THE CARNEGIE MUSEUM 
not distinctly recognized as such although clearly figured. Owing also to a palpable 
numerical error in the measurements of the cranium (‘.50 M. = 242 in.”) the total 
length of the original animal was estimated at thirteen feet, and is so referred to in 
text-books! The actual length is far less, as will clearly appear in the present 
description of a much completer cotype almost exactly the size of the original Cope 
specimen. ‘This error was, however, in a sense prophetic, as some of the turtles of the 
related Dakotan genus Archelon, discovered by the writer twenty-four years after the 
first Protostega, did actually reach, or possibly exceed, the enormous size of thirteen 
feet in length. 
Protostega remained a very vaguely known turtle until Baur?’ pointed out that 
it must in its main characteristics agree with the Cheloniide, and that the plates 
Cope supposed were dorsal must be plastral. That such was the fact was later more 
definitely shown by Hay,’ who figured the nuchal and hyo- and hypoplastron of 
another Niobrara specimen. 
The next contributions to our knowledge of the osteology of the Protostegine 
were made by the writer, after his discovery of gigantic turtles east of the Black 
Hills in the Fort Pierre Cretaceous in the summer of 1895. In the communica- 
tions,‘ which soon followed, the structure of the greater part of the carapace and 
plastron was made known from remarkably preserved specimens. All the larger 
limb bones were also determined and figured ; for the first time, indeed, in the case 
of any extinct sea-turtles of America. There immediately followed these papers the 
important contribution of Case,’ which, in addition to a careful discussion of the 
systematic position of Protostega, added more particularly to a knowledge of the 
cranial characters, as based on the description of various crushed, but otherwise well 
defined disarticulated elements. The pelvis was also made known. 
Further facts concerning the general cranial type in the Protostegine were next 
given by the writer® in a paper describing the splendid skull of Archelon, now on 
exhibition in the Yale Museum. Later an attempt was made by Williston’ to 
restore the tarsus and give the organization of the hind flipper of Protostega, and by 
2(a) ‘‘Die Systematische Stellung von Dermochelys Blainville,’’? Biolog. Centralblatt, IX., 1889. (b) ‘‘On the 
Classification of the Testudinata,’’ American Naturalist, XXIV., 1890. 
3“*On Certain Portions of the Skeletion of Protostega gigas,’’? Field Columbian Museum Publication, No. 7, 1895. 
4(a) “ Archelon ischyros, a New Gigantic Cryptodiran Testudinate from the Fort Pierre Cretaceous of South 
Dakota,’? Am. Jour. Science, December, 1895. (h) ‘The Protostegan Plastron,’’ Jbid., January, 1898. 
5 **On the Osteology and Relationships of Protostega,’’ Journal of Morphology, Vol. XIV. (This publication bears 
the date 1897, but did not appear until some time in June, 1898, its presumptively true date. ) 
®**The Skull, Pelvis, and Probable Relationships of the Huge Turtles of the Genus Archelon from the Fort Pierre 
Cretaceous of South Dakota,’’ Am. Jour. Sci., Vol. IX., April, 1900. 
7**On the Hind Limb of Protostega,’’ Ibid., Vol. XIII., April, 1902. 
