46 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 

 Measurements of anterior caudal vertebrae of Antrodemus valens, No. S367. 



The vertebral centra are concave on the sides and below. The first caudal 

 has a transverse rounded ventral surface, but in the succeeding caiuials as far back 



as the seventh, this surface is obtuse, but none 

 are longitudinally grooved in this aspect as in 

 Cerafosaurus. 



The articular faces of the centra are biconcave. 

 On the anterior caudals this concavity is most pro- 

 nounced on the anterior face, but in the mid caudal 

 region these faces become subequal. On both ends 

 the lower articular faces are beveled off for the 

 chevron articulation (fig. 28 cli^.). 



None of the neural spines are perfectly preserved, 

 the most perfect one is on the sixth caudal, as 

 shown in fi^gure 28. At the base it is wide from 

 front to back, heavy transversely, with a broken 

 upper extremity that is beginning to widen trans- 

 versely, thus indicating an expanded upper end. 

 The spines are inclined strongly backward, their 

 upper ends overhanging the posterior face of the 

 centra. Proceeding posteriorly the spinous pro- 

 ne. 2S.-SIXTH CAUDAL VERTEBRA Or .A.NTEO. ccsses gi'ow smallcr, SO that in the mecUan caudal 

 DEMus VALENS leidy, no. 8367, u.s.N.M. region it has been reduced to a short thin upstand- 



i N.iT. SIZE. Viewed from the left side. ., ., ., ^■ i ■ i 



mg plate oi bone without distal expansion as shown 

 in figure 29. In Ceratosaurus the last distinct spine 

 is on the thirty-first caudal; in Antrodemus, how- 

 ever, they must surely have disappeared forward 

 of that point. 

 The diapophyses or transverse processes in the anterior region have their 

 origin on the side of the neural arch, being directed outward, backward, and slightly 

 upward. In the anterior region they are long, outwardly exjianding processes that 

 come to rather of a square end distally. Dorso-ventrally on the outer end they 

 gradually thicken toward the point of attachment on the sides of the arch. A 

 caudal of No. 4734, U.S.N.M., intermediate in position between those vertebrae 



cA, facet fob chevron; d, diapophvsis: 2, 

 anterior zygapophysis: 2', posterior ztga- 

 popHYsis. This vertebral centrum was 

 sectioned as shown in plate 1, figs. 4, 5, 



AND 6. 



