PLATE XVII. 



Jurassic Dinosaurs. — Sauropoda. 



Atlantosaurid^e. 



Page. 



Fig. 1. Sacrum of Atlantosaurus montanus Marsh; seen froin below 166 



Fig. 2. Sacrum of Jpatosaurus ajax Marsh ; seen from below 166 



a, first sacral vertebra ; b, transverse process of first vertebra; c, trans- 

 verse process of second vertebra ; d, transverse process of third vertebra ; 

 e, transverse process of fourth vertebra;/,/',/", foramina between trans- 

 verse processes; g, surface for union with ilium; p, last sacral vertebra. 

 Both figures are one- tenth natural size. 

 278 



