OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



Measurements of presacral vertebrae of Antrodemus valens Leidi/. 



43 



<• Estimated. 



b Beginning of dorsal series. 



Sacral vertebrae. — Tke description to follow of the sacral vertebrae of Antro- 

 demus is based on the sacra of four individuals, Nos. 4734, 8405, 8423, and 8367, 

 arranged in the order of their importance, but more especially on the splendidly 

 preserved sacrum of No. 4734, U.S.N.M., shown in all aspects in plates 8, 9, and 10. 

 Three of these specimens each have five coosified vertebrae in the complete aacral 

 arcade. As in Tyramiosaurus and Ceratosaurus, Si, is directly opposite the pubic 

 peduncle of the articidated ilium (see pi. 9, fig. 2), wliile S3 is opposite the ischiac 

 peduncle. It is quite probable that S, and S3 represent the primary sacrals, S, 

 being a modified dorsal, and S4 and S5, modified caudal vertebrae. 



The five sacral centra have concave sides and ventral surfaces, though the 

 flange-like ends of the preceding dorsals are only found on the anterior end of S^ 

 Sj and S3 are much compressed transversely, with the ends little expanded. The 

 lateral depressions on the superior sides of the centra are present in all the sacrals 

 of No. 4732, but in the other individuals these depressions grow shallower from front 

 to the back of the series. 



The ilia are united to the sacrum by stout but exceptionally short sacral ribs 

 and by the transverse processes. There appear to be four distinct sacral ribs (pi. 

 8 sr.). These unite with the sacrals inter vertebrally. The anterior rib articu- 

 lates about equally with roughened facets on S^ S3, but the succeeding two are 

 supported more by the posterior centrum — that is, S3 and S^, respectively. The 



