SYSTEMATIC REVISION 



27 



other that the hyposphene-hypantrum articulation can not be seen from the side, 

 as in Dtadectes. The transverse processes are similar to those of Diadectes, having 

 single faces inclined downward and forward to the upper edge of the centrum. The 

 neural arches are free from the centra, which are detached in most parts of the 

 column. The lower edges of the neural arches are rounded and appear to have 

 been attached to the centrum by a considerable mass of cartilage. The centra are 

 deeply biconcave or notochordal; the lower surface can not be clearly made out, 

 but there seems to have been a broad, low median keel. No intercentra can be 

 made out, but small ones were undoubtedly present. 



Fig. 6. — Outline of part of vertebral column of Diadecloides cretin. X §. Univ. of Chicago. 



The sacral vertebra resembles the others in the neural arch and spine, except 

 that the posterior zygapophyses are reduced in size and this portion of the neural 

 arch is thinner. The transverse process, however, presents a very large face almost 

 directly downward, for the head of the sacral rib. The centrum is not attached to 

 that of the following vertebrae; there is no sacrum. 



Posterior to the sacral vertebra there are fourteen caudal vertebra. The apices 

 of the spines of the first are more elongate oval and they rapidly decrease in size. 

 The transverse processes do not have elongate faces slanting forward and downward, 

 but round, rather large faces looking outward but largely downward. Chevrons 

 appear on the fourth or fifth; these are short, bifurcate above, and inclined to the 

 rear. The neural arches and centra are narrower in this region and the whole tail 

 was flat and high. 



The ribs are single-headed, long, and slightly curved; free ribs occur on all the 

 presacral vertebrae preserved; there were no true lumbars. The sacral rib is very 

 short and heavy; the proximal end was attached by two wide faces to the transverse 

 process and the centrum; there is practically no shaft and the distal end is expanded 

 into an elongate oval, with its main axis vertical, applied to the inner side of the 

 ilium. The first caudal ribs were free, but they soon disappear. 



The ilium is short and stout with a slightly convex anterior edge and a promi- 

 nent posterior projection. A good-sized process overhangs the acetabulum. The 

 attachment of ischum and pubis was sutural. 



The femur is exceptionally short and strong. The upper end presents a nearly 

 flat articular face; there is a prominent process on the posterior face near the anterior 



3 



