AET. 16 



FOSSIL EEPTILES FROM MOISTTANA GILMORE 



17 



The transverse processes of the posterior dorsals appear, when 

 viewed from the end, to originate far down on the side of the arch, 

 but this is brought about by the fusion of the rib heads with the 

 parapophyses, as shown in Figure 11, whereas in reality these proc- 

 esses originate some distance above. The posterior dorsals of Anky- 

 losaurus are even more deceptive in this respect. 



Measurements of dorsal t'ertehrae 



Greatest length of centrum 



Greatest height of centrum, posterior end 



Greatest height over all 



Greatest expanse of transverse process 



Anterior 



Middle 



Mm. 



Mm. 



65 



83 



97 



95 



235 



1 258 



248 



200 



Posterior 



Mm. 

 68 

 100. 5 



180 



1 Estimated. 



Sacrum. — The sacrum of Palaeoscincus rugosidens consists of three 

 sacral vertebrae in the primary sacrum, four presacrals (sacro- 

 lumbars), and two sacro-caudals, all coalesced into a synsacrum com- 

 plex of nine vertebrae in all. This is the same number and arrange- 

 ment as in Nodosaurus textilus as described by Lull.^^ In P. ru- 

 gosidens only the ventral surface of the sacrum is preserved, as 

 shown in Plate 4. The upper side was eroded away before the final 

 entombment of the skeleton. Viewed laterally the sacrum complex 

 is bowed from end to end, especially posteriorly. The centra are 

 so firmly coossified that the line of demarcation between successive 

 vertebrae has practically been obliterated. The usual dilaaon of 

 the ends of the centra is missing, hence no clue is to be had from 

 that feature. Ventrally the sacrum is characterized by a longitudinal 

 groove that traverses all except the first two sacro-dorsals and the 

 last sacro-caudal. 



The anterior coosified centra are relatively long and slender, broad- 

 ening into a wide plate in the true sacral region, narrowing again in 

 the sacro-caudal region. The three sacrals bear long, relatively slen- 

 der ribs which are coossified to their respective centra, their lower 

 margins being on the same level as that of the centra. The expanded 

 distal ends are coossified, especially one and two, together forming 

 the sacricostal yoke which abuts against the inner side of the ilium. 

 Dorsally these ribs appear to have been continuous with the cliapo- 

 physial lamina. 



The transverse processes are lacking in the first sacro-caudal, but 

 in the second they are preserved as long, slender processes origi- 



"Amer. Journ. Sci., vol. 1, 1921, p. 102. 

 2601—30 2 



