99 



Measurements. 



M. 



Length of the coracoid 0.250 



Width of the coracoid distally 0.080 



Length of the ramus of the mandible 0. 157 



Length of the symphysis of the mandible 0. 031 



Elevation of the coronoid of the mandible 0.043 



Width of the angle of the coronoid 0.023 



The axes of the mandibular rami produced unite at an angle of 65°, 

 indicating a muzzle of intermediate length. 



The size is about that of the existing loggerhead (Caretta caouana). 

 Found by Professor Mudge near the forks of the Smoky Hill River. 



J6 



15 



Fig. 2. — Sketch of the large radiated bone of Protostcga gigas, with other elements, as they were 

 uncovered by excavation; size much reduced, drawn on the spot. Nos. I, VII, VIII, and IX, costal 

 bones, with the rib-heads looking upward ; X, the coracoid bone ; 5, a marginal bone ; 9 and 10, the lateral 

 a radiate bones; 16, vertebra, with other bone adherent. 



PROTOSTEGA, Cope. 



This genus is the type of a new family of tortoises of the suborder 

 Athecce, characterized by the lack of expansion of the ribs into a bony roof, 



