OSTEOLOGY OF THE ARMOKED DINOSAUEIA. 

 Measurements of sacral and presacral vertebr.ae of Stegosaurus stenops. No. 4934. Type. 



53 



Vertebrae. 



Greatest 

 length of 

 centra. 



Greatest 

 trans- 

 verse 

 diameter 

 posterior 

 ends. 



Greatest 

 height 

 over all. 



Atlas 



■mm. 

 32 

 56 

 66 

 82 



104 

 96 

 99 

 93 

 S4 

 87 

 73 

 74 

 70 

 75 

 S2 

 85 



mm. 

 56 



mm. 







3 







4 



61 

 67 

 80 









6 





7 



135 



S 





9 







10 







11 







12 







13 







14 







15 







16 







17 







18 









19 



20 



lOle 

 105 

 102 

 101 

 102 

 97 

 85 

 70 

 169 



72 

 69 

 75 



78 





430 

 458 

 430 





21 



68 

 76 



22 



23 





24 



86 

 104 



76 





25 





26 









Sacrals: 



I. . . 







II 



Ill 







102 

 116 





Sacro-caudal 







i Estimated. 



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. stenops, 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 l 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, in Nos. 6531 and 73S6 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 



1 Amer. Journ. Sci., vol. 21, pt. 4, 1881, p. 168, fig. 1, pi. 7. 

 51873°— Bull. 89—14 5 



