OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



47 



illustrated in figures 28 and 29 has the left process almost perfectly preserved. It 

 is thin dorso-ventrally without especial distal expansion and extends directly 

 outward from the superior median side of the centrum. 



Further back, as shown in figure 29, the transverse process is still further 

 reduced in size and its position has shifted downward to the middle of the centrum. 



Fig. 29.— Median caudal vertebra of Antrodemus valens Leidy. No. 8367, U.S.N.M. J nat. size. Viewed from the 



LEFT SIDE. S, SPINOUS PROCESS; 2, ANTERIOR ZTGAPOPHYSIS; z' , POSTERIOR ZYGAPOPHYSIS. 



In all probability it would have entirely disappeared on the second or third vertebrae 

 posterior to this one. 



Concurrent with the reduction 

 of the transverse processes there 

 is a great enlargement and pro-, 

 longation of the anterior ?yga- 

 pophyses, as shown in figures 

 29 and 30. These zygapophyses 

 have wide expanding ends which 

 stand high above the centrum 

 with inner faces that look almost 

 directly inward. More posteri- 

 orly (fig. 30) the upward incli- 

 nation is less and the zygapo- 

 physes gradually narrow in width dorso-ventrally to its free end. More posteriorly 

 still, as shown in figure 31, the anterior zygapophyses become more rod like, though 

 their great anterior prolongation is maintained. These are in striking contrast to 

 the comparatively weak zygapophyses of the Ceratosaurus caudals, but very similar 

 in those of Gorgosaurus and Omithomimus. 



Fig. 30.— Caudal vertebra from distal fourth of the tail of Antro- 

 demus valens Leidy. No. 4734, U.S.N.M. 4 nat. size. Viewed from 



RIGHT SIDE. 2', ANTERIOR ZYGAPOPHYSIS; 2, POSTERIOR ZYGAPOPHYSIS. 



