173 



the neural arch. It ends in a flat, roughened articular surface, as if intended 

 for the conjunction of another vertebra entering into the constitution of the 

 sacrum. The neural arches of the sacral vertebrae are proportionately higher 

 than in the snapper, and they appear to have articulated movably with each 

 other by zygapophyses alone. 



The diapophyses are about equally developed with those in the snapper. 

 The neural arch is not co-ossified with the centrum ; nor are the pleurapophyses 

 co-ossified with either. 



Measurements of the sacral vertebse are as follows : 



Lines. 



Length, of the sacrum inferiorly 18 



Length of first sacral centrum 7 



Breadth of first sacral vertebra, with diapophyses 9 



Length of second sacral centrum 11 



Breadth of second sacral vertebra, with diapophyses 10.] 



Height of first sacral vertebra to end of spinous process 13 



Height of anterior articulation of first sacral centrum 5 



Breadth of anterior articulation of first sacral centrum 5 



An isolated vertebra, from Henry's Fork of Green River, looks as if it 

 might be the first sacral of Chisternon undatum. The body is little more than 

 half the length of that of the last sacral above described, but its anlcrior 

 articular surface agrees in size, form, and roughness with the posterior sur- 

 face of the last sacral centrum just mentioned. The pleurapophyses have 

 about the same degree of development as in the snapper. 



Fig. 10, Plate XVI, represents a caudal vertebra, obtained by Dr. Carter 

 near Lodge-Pole Trail. In construction it resembles the caudals of the 

 snapper, the centrum, as in this, being opisthocoelian, or having a cup behind 

 and a ball in front. The proportions of the vertebra accord best with the 

 more anterior caudals of the snapper, but its transverse processes are as small 

 as in the terminal caudals of the latter. Perhaps it may belong to Chister- 

 non, but the opinion is conjectural. If the former isolated vertebra belongs 

 to Chisternon, it is doubtful whether this second one does. 



Fig. 7, Plate XVI, represents an isolated ilium of a turtle, found at Grizzly 

 Buttes by Dr. Carter. It resembles in its form that of a snapper, but is more 

 robust in proportion to its length. The inner surface at the upper extremity 

 is flat and longitudinally striated, but is devoid of the fossa existing in the 

 snapper. The length of the bone is 3| inches ; the width of its upper end 

 % of an inch ; the width at the lower end is 17 lines. From the form of the 



