172 



DINOSAURS OF NORTH AMERICA. 



solid throughout, and the same is true of the chevrou, tigs. 4 and 5. 

 The ueural spines of the anterior caudal vertebra; are elevated and 

 massive. The summit is cruciform in outline, due to the four strong 

 buttresses which unite to form it. 



The median caudals all have low, weak spines, and no transverse 

 processes. The posterior caudals are elongate and without spines or 

 zygapophyses. 



THE PELVIC ARCH. 



The pelvic bones in the present species are shown in fig. 16. The 

 ilium represented is not quite perfect on its upper margin. Its ante- 

 rior process for the support of the pubis is much larger than the poste- 



Fig. 16.— Pelvis of Brontosaurun excelsus; seen from tbe left. One-sixteenth natural size. 

 a, acetabulum; /, foramen in pubis; £2, ilium; w, ischium; p, pubis. 



rior one which meets the ischium. The pubis is elongate and massive. 

 It sends down a strong wing for union with the ischium, and has in 

 front of this the usual foramen. The distal end is expanded, and has 

 on the inner surface a rugose facet for union with its fellow by cartilage. 

 The ischium is more slender than the pubis, and has its lower end 

 expanded for symphysial union with the one on the other side (PL 

 XXIV, figs. 1 and la). This pelvis is more like that of Atlantosaurus 



