198 



Prof. 0. C. Marsh — Oigantic Ceraiopsidce. 



Fig. 7). The middle or true sacral vertebrfe have double transyerse 

 processes, diapophyses being present, and aiding in supporting the 

 'ilium. This character has been seen hitherto, in the Dinosauria, 

 only in Ceratosaurus and some other TJieropoda. 



The main support of the pelvis was borne by four vertebrae, 

 which evidently constituted the original sacrum. In front of these, 

 two others have only simple processes, and apparently were once 

 dorsals or lumbars. Three vertebrae next behind the true sacrum 

 have also single processes, and the fourth, or last of the series, has 

 the rib process weak, and not reaching the ilium (Woodcut, Fig. 7). 

 Seen from the side, the sacrum is much arched upward, and the 

 neural spines of the true sacrum are firmly coossified. In the 

 median region, the sacral vertebras have their centra much com- 

 pressed, but the last of the series are widely expanded transversely. 

 The whole appearance of the sacrum is remarkably avian. The 

 neural canal of the sacral vertebrae has no special enlargement, thus 

 differing widely from that in Sfegosaurus. 



The Caudal Vertebra. — The caudal vertebrae are short, and the 

 tail was of moderate length. The first caudal has the anterior face 

 of the centrum concave vertically, but flat transversely, and a short, 

 massive neural spine with expanded summit (Woodcut Figs. 8-10). 



Fig. 8. — First caudal vertebra of Triceratops prorsus, Marsh; side view. 

 Figs. 9, 10. — Front and back views of same vertebra. 



Fig. 11. — Median caudal of same species, side view. 

 Figs. 12, 13. — Front and back views of same vertebrae. 



a. anterior face of centrum ; c. face for chevron ; n. neural canal ; 



p. posterior face of centrum ; r. rib ; s. neutral spine ; a. anterior 



zygapophysis ; z'. posterior zygapophysis. 



