46 



BULLETIN" 110, UNITED STATES NATIONAL MUSEUM. 

 Measurements of anterior caudal vertebrae of Antrodemus valens, No. 8367. 



Number 



Length at 



Width ante- 



Height ante- 



of 



center of 



rior end 



rior end 



vertebra . 



centrum. 



of centrum. 



of centrum. 





mm. 



mm. 



mm. 



1 



121 



133 



138 



2 



123 



133 



140 



3 



125 



123 



130 



4 



120 



113 



126 



5 



118 



115 



115 



6 



120 



112 



115 



7 



120 



95 



97 



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

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



as the seventh, this surface is obtuse, but none 

 are longitudinally grooved in this aspect as in 

 Ceratosaurus. 



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 ch.). 



None of the neural spines are perfectly preserved, 

 the most perfect one is on the sixth caudal, as 

 shown in figure 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- 

 cesses grow smaller, so that in the median caudal 

 region it has been reduced to a short thin upstand- 

 ing plate of 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 expanding 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 



Fig. 28.— Sixth caudal vertebra of Antro_ 

 demus valens i/eidy, no. 8367, tj.s.n.m. 

 J nat. size. Viewed from the left side. 



eft, FACET FOR CHEVRON; d, DIAPOPHYSIS; Z, 



anterior zygapophysis; z', posterior zyga- 

 pophysis. This vertebral centrum was 

 sectioned as shown in PLATE 1, FIGS. 4, 5, 

 AND 6. 



