EXPLANATION OF PLATE 15. 



Shastasaurus altispinus n. sp. 



All figures are from the ti/jie specimen, and are represented three-fourths 



■natural size. 



Fig. 1. — Centrum of posterior dorsal vertebra, showing the long, con- 

 stricted diapophysis separated from the superior articular 

 surface. 



Fig. 2. — Centrum of a middle dorsal vertebra. The articular surface of the 

 diapophysis is directly connected with that on the superior side 

 of the centrum. 



Fig. 3. — Posterior view of the spine of a dorsal arch. 



Fig. 4. — Cross-section of the spine shown in figure three. The section is 

 taken through the plane indicated by dotted lines on figure three. 

 r indicates posterior side of spine. 



Fig. 5. — Articular surface of head of a left dorsal rib. 



Fig. 0. — Posterior side of head of a right dorsal rib. 



