iSS 



FOSSIL TURTLES OF NORTH AMI RICA. 



Cope was the first to refer the hone to the turtles, and he placed it in his genus Protostega. 

 At a little later time Leidv referred it to Atlantochelys. In 1889 Baur correctly concluded 

 that it could belong to neither Protostega nor to Atlantochelys, but he did not name the genus. 

 This was reserved for Wieland to do in 1900. 



The total length of the humerus (fig. 244) is 10 inches, or 253 mm. The shaft, where 

 narrowest, is 48 mm. wide and 28 mm. thick. The distance from the extremity of the ulnar 

 process to that of the radial process was estimated to be 152 mm. The breadth ot the distal 

 end is 95 mm.; the thickness. 50 mm. The form of the bone is shown bv the figure, copied 

 horn Leidy. 



Genus ATLANTOCHELYS Agassiz. 



A genus based on the proximal end of a humerus of a sea-turtle. The head and the ulnar 

 and radial processes in approximately the same plane. Radial process hardly separated from 

 the head. Ulnar process directed nearly parallel with axis of bone. Shaft unusually slender. 



Type: Atlantochelys mortont Agassiz. 



Fig. 244. Neptunochelys tuberosa. 

 Humerus forming the type. X^. 



Fig. 245. Atlantochelys mortoni. Portion of humerus 

 forming the type. Xij. After Leidy. 



Atlantochelys mortoni Agassiz. 

 Fig. 245. 



Atlantochelys mortoni, Agassiz, Proc. Acad. Nat. Sci. Phila. 1849, p. 169 (no description); in Leidv, 

 Smithson. Contrib. Knowl., xiv, art. vi, 1865, p. 43. Leidy, Ext. Vert. Fauna West. Tens., 

 1872, p. 342. Wieland, Amer. Jour. Sci. (4), 1900, p. 419, tigs. 14-16. Hay, Amer. Naturalist, 

 xxxil, 1898, p. 930; Bibliog. and Cat. Foss. Vett. N. A., 1902, p. 440. 



Mosasaurus mitchelli, Leidy, Smithson. Contrib. Knowl., xiv, art. vi, 1865, 43, 117, plate viii, tigs. 3-5. 



Protostega neptunia, Cope, Fifth Ann. Report U. S. Geol. Surv. Terrs., 1871 (1872), p. 334; Proc. Amer. 

 l'hilos. Soc, XII, 1872, p. 433; Vert. Cret. Form. West, 1875, p. 257. 



Like Neptunochelys tuberosa, this species is based on a humerus which was derived from 

 the Upper Cretaceous formation. The exact locality and level were not reported, but we 

 know that the fossil was found in one of the beds of Cretaceous greensand in Burlington 

 County, New Jersey. 



( )t this humerus (fig. 245) there was secured only the proximal half or less. This fragment 

 had a length of about 280 mm. The shaft was extremely slender, being /$ mm. wide and 

 60 mm. thick. The ulnar process rises above the head about 75 mm. The radial process is 



