202 



REPTILIA. 



it. The whole of the sacrum is hollow, the cavity in the fused centra 

 being partially divided by a median longitudinal partition. The elevated 

 neural spines of the sacral vertebrae are fused into a large vertical plate 

 with thickened summit. The caudal vertebrae are solid, the three anterior 



Brontosaurus excelsus; pectoral arch, anterior aspect, one-sixteenth nat. size, 

 with sternum of young ostrich (Struthio camelus) for comparison (fig. 

 122 A). Jurassic; Wyoming, c, coracoid; ct., sternal cartilage; g, glenoid 

 cavity for humerus; os., sternal bone; s, scapula; sr., sternal ribs. (After 

 Marsh.) 



caudals alone excavated at the side. The scapula (fig. 122, s) is expanded 

 at its base, but slender distally ; the coracoid (c) exhibits a small perfora- 

 tion. A single pair of smaller bones (os.) are interpreted as ossifications 

 in the sternal cartilage. In the pelvic arch the pubis is more robust than 



