G. R. Wieland — Upper Cretaceous Turtles. 189 



and the Osteopyges, which are broadest across the anterior end 

 of the sixth neural. In the present more primitive turtle 

 the cordate form of the Chelonine carapace is beginning to 

 appear, the swinging back of the eighth rib into a pit of the 

 eleventh marginal, and the consequent leaving of the tenth 



Figure S.—Lytoloma angusta Cope (Yale specimen 625). Natural size. 

 Vertical middle transverse section through the 4-11, and pygal (pm) mar- 

 ginals. Eespective rib pits in dotted outline. 



marginal without a supporting rib, as in Chelone, having 

 already occurred. Compare plates V and VI. In Osteopygis 

 Gihbi the femur is longer than the humerus, and from general 

 comparison it may be argued that in the present species of Lyto- 

 loma the femur is relatively shorter than in Osteopygis, but not 

 so shortened as in the existing marine turtles. This inter- 

 mediate development is an important point. . 



