234 



WATER REPTILES OF THE PAST AND PRESENT 



Later studies by Doctors G. Baur, E. C. Case, O. P. Hay, and 

 especially G. R. Wieland, of the abundant and excellent material, 

 preserved in the museums of Yale and Kansas universities and 

 the Carnegie Institution, and especially the discovery by Wieland 

 in 1895 of an allied and yet larger form which he called Archelon, 

 have determined practically every detail of the structure of this 

 remarkable group of sea-turtles. A surprisingly complete speci- 

 men of Archelon is mounted in the museum of Yale University. 



Fig. 123. — Archelon ischyros; skeleton from above: n, nuchal, r, r, r, ribs; m, m, 

 peripheral bones; h, humerus; r, radius; n, ulna; /, tibia; fi, fibula. (From Wieland.) 



About a half-dozen species and two genera of the family have 

 so far been described, all coming from the Upper Cretaceous 

 deposit of Kansas and South Dakota, the genus Archelon from later 

 rocks than those which have yielded Prolostega. 



The general form and structure of Archelon will best be under- 

 stood from the accompanying figures after Wieland (Figs. 123, 

 124, 125) and the restoration of the living animal as interpreted 

 by the writer (Fig. 126). If the leather-back turtle, described 



