168 



MAEINE EEPTILES OE THE OXPOED CLAT. 



vertebra the spine is still thickened, but is nearly vertical : it terminates above in a 

 convex facet, which does not occupy the whole length of its upper end ; in this vertebra 

 also the zygapophyses are much reduced. The next vertebra (the first of those in the 

 deflected portion of the tail) has a much higher neural spine, which is directed 

 forwards ; in the next the spine is likewise large, much thickened at its upper end, and 

 directed forwards. The anterior zygapophyses are well developed and articulate with 

 the small posterior zygapophyses on the posterior face of the arch in front. Behind 

 this point the neural spines become smaller and smaller, but are still directed forwards. 

 A little in front of the flexure of the tail the centra become strongly compressed from 

 side to side, and at the flexure itself they are considerably longer dorsally than ventrally, 



Test-tig. 67. 



I±Z 



Eibs of MetrlorhyncTius svperciliosum : A, right rib of axis ; B, right rib of atlas ; C, middle right cervical 

 rib ; D & E, anterior dorsal ribs ; E, middle dorsal rib. (E. 1530, if uat. size.) 



d., diapophysial process (tubercle) ; p., parapophvsial process (bead). 



the flexure being, in fact, produced by the apposition of the centra of this form. 

 Behind the flexure there seem to have been about thirteen vertebra?, the centra of 

 which are all strongly compressed laterally. 



Bibs (text fig. 67). — The rib of the atlas (text-fig. 67, B) is a simple bar of bone 

 which widens a little in its posterior third and then narrows posteriorly to a blunt 

 point. At its anterior end it bears a flat, or slightly convex, facet for union with the 

 corresponding surface on the posterior border of the anterior subvertebral wedge-bone ; 



