73 



In the middle dorsal region the transverse processes lose these 

 thin projections, and become heavy and subtrihedral, with a* 

 smooth facet on their lower face for articulation with the 

 tubercle of the rib ; their upper face is here a little twisted 

 from the plane of the laminae. In the posterior dorsal region 

 the transverse processes lose the facet for the articulation with 

 the tubercle of the rib, and become short and very thin, point- 

 ing slightly backwards. 



The lumbar transverse differ from those of the last dorsal 

 in having a median transverse ridge on their posterior face, 

 and are directed more vertically out. 



The pedicles throughout most of the dorsal series are 

 short, heavy, and deeply notched behind. In the posterior 

 dorsal region they become longer and more slender, resem- 

 bling almost exactly the pedicles of the lumbar region. 



Sacral region. The sacrum is composed of four vertebrae, 

 three true and one pseudo-sacral. The centra are extremely 

 depressed, and rapidly decrease in width and thickness from 

 before backwards. The first is shorter than the last lumbar, 

 but much longer than the other sacrals, which are subequal. 



The face of the first is elliptical, and is nearly three times 

 the diameter of the fourth, longitudinally. The metapophy- 

 ses are exceedingly large and tuberous on the first ; with 

 wide, deeply concave pre-zygapophyses developed upon 

 them ; in the other three the metapophyses are rudimen- 

 tary. 



The transverse processes are long and wide in the first 

 three ; widest in the first but thickest in the second ; long and 

 thin in the fourth. The pleuropophysial segments of the true 

 sacrals are very heavy. 



The foramina enclosed by the transverse processes are 

 large ; and have, on the internal side, their long diameter 

 obliquely transverse to the axis of the sacrum. 



The inferior faces of the centra are slightly concave in the 

 first three. The first and fourth have slight hypophysial 

 keels. 



The neural canal is very wide and depressed in the first, 

 but decreases rapidly backwards, becoming extremely small 

 in the last. 



