G. E. Wieland — On Marine Turtles. 99 



II. The Front Flipper of Archelon ischyros. 



In my first description of the gigantic turtle skeleton from 

 the Fort Pierre Cretaceous of South Dakota which constitutes 

 the type of Archelon ischyros,'^ I figured, in addition to other 

 skeletal parts, the humerus, radius, uhia, femur, tibia, and 

 fibula, and mentioned the fact that a number of carpals and 

 tarsals with several phalanges were also present. This was 

 practically the first contribution presenting the main features 

 in the limb organization of the [Protosteginse]. Hitherto our 

 knowledge of the flippers of these great turtles had been lim- 

 ited solely to that given in Cope's original description of the 

 first member of the group discovered, Protostega gig as. ^ h\ 

 this form the humerus was described and figured together with 

 the radius and ulna, although the latter were then supposed to 

 be " metapodials " rather than bones of the forearm. 



As there ^vas at the time of my first publication an absolute 

 dearth of information concerning the carpal and tarsal structure 

 in marine turtles from the American Cretaceous, not one hav- 

 ing been described, the fear that I might make some serious 

 error prevented my publishing the restoration of the carpus 

 which I then made, the various elements having been found 

 only partly in position. 



JS'ow^ however, Professor Willistonij: has just described the 

 hind flipper of Protostega., and this enables me by exclusion 

 to determine with a reasonable assurance of correctness that the 

 elements [ originally assigned to the carpus in my study of the 

 closely related Archelon truly belong tliere. I am hence able 

 to add some further facts concerning the skeletal organization 

 and systematic position of these highly interesting Testu- 

 dinates. 



The partial restoration of the left fore flipper shown in 

 figure 2 is based on the radius and ulna, with what are consid- 

 ered to be all of the carpals but two, together with the first 

 and fifth metacarpals. Several phalanges are present, but as 

 finger proportions may vary markedly it is not deemed advis- 

 able to attempt a complete restoration. The value to be 

 attached to this preliminary restoration is provisional, as 

 follows : 



(a) The radius and ulna are simply drawn in a generalized 

 position, but their orientation is based on that found in a sec- 

 ond specimen where these bones w^ere in an approximately 

 normal position with respect to the humerus, only. 



*G. E. Wieland. — A New Gigantic Crj^todire Testndinate from the Fort 

 Pierre Cretaceous of South Dakota. This Journal, fourth series, vol. ii, 

 December 1896. 



f Loc. cit. 



X S. W. Williston.— On the Hind Limb of Protostega. This Journal, fourth 

 series, vol. xiii, April, 1902. 



\ /" 



