OSTEOLOGY OF THE AEMOEED DINOSAUKIA. 53 



Measurements of sacral and presacral vertebrae of Stegosaurus stenops. No. 4934. Type. 



Vertebrae. 



Greatest 

 length or 

 centra. 



Greatest 

 trans- 

 diameter 

 posterior 

 ends. 



Greatest 

 height 

 over all. 





Atlas 



vim. 

 32 

 56 

 66 

 82 

 104 

 96 

 99 

 93 

 84 

 87 

 73 

 74 

 70 

 75 

 82 

 85 



56 



mm. 





Axis 







3 









4 



61 

 67 

 80 







5 







6 : 







7 



135 





8 







9 









10 









H 









12 









13 









14 









15 









16 









17 









18 











19 



lOle 

 105 

 102 

 101 

 102 



97 



85 



70 

 ■69 



72 

 69 

 75 



78 





430 

 468 

 430 





20 







21 



68 

 76 





22 





23 







24 



86 

 104 

 76 







25 







26 







27 Dorso-sacral 







Sacrals: 



I 









II 









Ill 



102 

 116 







Sacro-caudal 













/Sacrum.— The following description of the Stegosaurus sacrum is based upon 

 the sacra of five individuals in the National Museum, but more especially upon the 

 well preserved articulated pelvic arch pertaining to the type of S stenovs No 4934 

 (fig. 23). ■ ' ' ■ 



In the sacral region of this specimen there are five coossified vertebrae but for 

 reasons to be given later three only are considered as pertaining to the true or 

 primary sacrum. In describing ' the sacrum of S. ungulatus Marsh found six verte- 

 brae coalesced, four of which he considered as true sacrals (fig. 22). In specimen 

 No. 7346 there are three coossified centra, m Nos. 6531 and 7386 there are four each, 

 and in No. 4936 there are six. From this evidence it would appear that in fully 

 adult animals the pelvic arch may be strengthened by the addition of one or more 



I Amer. Joum. Sci., vol. 21, pt. 4, 

 51873°— Bull. 89—14 5 



, p. 168, fig. 1, pi. 7. 



