184 



DINOSAURS OF NORTH AMERICA 



vertebrae are much longer than the corresponding vertebra? of Moro- 

 saurus, and have a very long, deep cavity in each side of the centrum, 

 to which the generic name refers. All the trunk vertebrae hitherto 

 found are proportionately nearly double the length of the corresponding 

 centra of Morosaurus, and the lateral cavity is still more elongate. 

 These points are shown in the posterior dorsal vertebra represented in 

 figs. 4 and 5 of PI. XL. The neural arch in this region is lightened by 

 cavities, and is connected with that of the adjoining vertebras by the 

 diplosphenal articulation. A dorsal centrum of another species is 

 shown below in tigs. 35-37. 



The sacral vertebrae in Pleuroccelus are more solid than in Moro- 

 saurus, but more elongate. The surface for the rib, or process which 

 abuts against the ilium, is well in front, more so than in any of the known 



Fig. 35.— Dorsal vertebra of Plettroccelus montanus Marsh ; side view. 

 Fin. 36. — The same vertebra; top view. 

 Fig. 37.— The same; back view. 



:;s 



39 



40 



41 



Fig. 38.— Caudal vertebra of same individual; froDt view. 



Fig. 39.— The same vertebra; side view. 



Fig. 40.— The same: bark view. 



Fig. 41. — The same; top view. 

 • All the figures are one- half natural size, a, anterior end;/, cavity in centrum; 7i, neural canal; 

 y, posterior end. 



Sauropoda. Behind this articular surface is a deep pit, which somewhat 

 lightens the centrum. These characters are seen in the sacral vertebra 

 represented in tigs. 0' and 7 of PI. XL. 



The first caudal vertebra has the centrum very short, and its two 

 articular faces nearly Hat, instead of having the anterior surface deeply 

 concave, as in the other known Sauropoda. An anterior caudal is 

 shown in figs. 38-41, above. The neural spines in this region are com- 

 pressed transversely. The middle and distal caudals are comparatively 

 short and the former have the neural arch on the front half of the 

 centrum, as shown in figs. 8 to 11 of PI. XL. 



The bones of the limbs and feet preserved agree in general with those 



