EXPLANATION OF PLATE 18. 



All specimens from the I'pper Triassic of Shasta County, California. 

 All figures four-ninths of natural size. 



Fig. 1. Sliastasattnis iiltispinus Merriam. Middle dorsal centnini. no. 9083. 



Figs. 2a and 26. Sltastasaurns altispinus Merriam. Neural arch of dorsal vertebra, no. 9083. 

 2a, lateral view ; 2b, anterior view. 



Figs. 3a and 36. Sliastasaurus altispinus Merriam. Head of a right dorsal rib, no. 9083. 

 3a, articular face; 35, posterior side. 



Fig. 4. fHia.it(isaun(.i altispinus Merriam. Klement from podial region, no. 9083. 



Figs. oa, 56, and 5c. Shastasaurus cnreyi (?) Men-lam. Middle dorsal vertebra, no. 9614. 

 5a, lateral view of vertebra; 56, top of nenral spine; 5c, anterior view of neural arch. 



Fig. 6. Shastasaurus careyi ( ?) Merriam. Posterior view of a dorsal rib, no. 9614. 



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