jici^&im^ 



THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.l 



Art. LYII. — Archelon ischyros : A new gigantic Cryptodire 

 Testudinate from the Fort Pierre Cretaceous of South 

 Dakota ; by Geo. R. Wieland. With Plate YI. 



Although it is now some twenty years since Cope first 

 described the genus Protostega, little or nothing has been added 

 to our knowledge of it by the description of new American 

 species. And. save the Italian Protosphargis of Capellini this 

 branch of the Sphargididse has remained a quite isolated one. 



I, therefore, propose to describe at this time certain portions 

 of a new gigantic testudinate closely allied generically, from 

 the Fort Pierre Cretaceous of South Dakota, for which the 

 name Archelon ischyros is proposed. 



The skeleton consists of carapace complete with ribs nearly 

 entire, the procoraco scapulars and coracoids, one humerus com- 

 plete, both femurs, radius and ulna, tibia and fibula one each, 

 a number of carpals and tarsals, a number of phalanges, most 

 of the cervical and caudal vertebrae, all the dorsal vertebrae, the 

 pelvis entire, a nearly or entirely complete set of spine set 

 plastral shields, fragmentary marginals, and certain bones 

 whose reference has not as yet been decided upon. 



As all the larger bones were found in place and the material 

 for a restoration is so exceptional, — one will be given in a short 

 time. 



General description. 



Carapace. — The carapace is composed of nine pairs of pleura- 

 lia, and eight medial pairs of plates or neuralia, followed- by one 

 single medial plate and the pygal, or 36 in all. These plates are 

 all very thin and of finely striate surface. They unite very 



Am. Jour. Scl— Fourth Series, Vol. II, No. 12.— December, 1896. 

 . 29 



