44 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



fourth rib assumes a higher and more posterior position and extends outward and 

 upward from about the center of Sj. 



In No. 4734 a notch separates the outer expanded diapophysial ends of Sj 

 and S3 from the distal ends of the sacral ribs as shown in plate 8, but in No. 8405 

 they form continuous articular ends for union with the ilium. Internal to the 

 distal ends they are joined by suture, as they do in the Sauropoda by a thin diapo- 

 physial lamina sent down from the underside of the diapophysis. The complete 



Fig. 27.— Fourteenth or last dorsal vertebra of Antrodemus valens Leidy, No. 8307, U. S. N. M , i nat. size. 

 A. SIDE view. B. front view, (f, diapophysis; p, parapophysis; z, anterior zygapophysis; 2', posterior 



ZYG.\POPnYSIS. 



union of these ends in S4 and S5 is well shown in jdate S, where they are seen to also 

 unite with one another at the top. The tliirtl rib is the stoutest and heaviest of the 

 series. 



The neural spuies are all united to form a continuous plate. Though coossifi- 

 cation has led to complete obliteration of the sutures theii' line of union can be 

 clearly determined by indentations along the top. The neural spines of the three 

 anterior sacrals are below the level of the ilia and can not be seen from a lateral 

 view; but in Ceratosaurus the first, as shown in plate 30, projects well above 



