410 



ME. ST. GEOEaE MIVAET ON THE 



The postaxial aspect of the centrum shows an articular surface which may be more 

 quadrate, its ventral margin often less preponderating over its dorsal margin than in 

 the preceding vertebra. The latter is also less concave, while the former is nearlj' 

 straight and may even be very slightly convex. 



The ventral surface has its preaxial margin more expanded and less sharply concave, 

 and its postaxial margin often less convex than is the case with the eighteenth vertebra. 



The hypapophysis is a single rounded, obtuse tubercle. It extends rather more 

 ventrad and sometimes less preaxiad than does that of the preceding vertebra. The 

 under siu'face of the centrum may be concave antero-posteriorly in the middle line 

 behind the hypapophysis. 



NINETEENTH VERTEBRA (| natural size). 



Fig. 43. Fig. 44. 



Aspects. 

 Fig. 42, lateral ; 43, preaxial ; 44, dorsal. Letters as before. 



The ventral aspect of the hj'papophysis exhibits, as it were, a slight lingering- 

 tendency to bifurcate. 



Behind the hypapophysis the surface of the centrum begins to be slightly convex 

 transversely instead of being concave. 



Not only is there, as has been said, no pleurapophysial band of bone, but no ridge 

 runs postaxially from the parapophysis, the side of the centrum being continued unin- 

 terruptedly dorsad into the side of the neural arch, the whole forming one concavo- 

 convex expanse. 



The ^Mrapophysis extends preaxially and slightly outwards, and has at the outside of 

 it a small, rather deep, concavity for the head of the rib, and on its inner side the lateral 

 continuation of the preaxial central articular surface (fig. 42, p). 



The diapophysis projects slightly more outwards from the prezygapophysis, is more 

 antero-posteriorly extended ; and the dorso-veutral distance between it and the parapo- 

 physis is greater than heretofore, extending to the preaxial margin of the neural 

 lamina. From its ventral outer side, near its preaxial end, the diapophysis develops a 

 rounded prominence (fig. 42, d) to receive the tubercle of the rib. Beneath it the 

 preaxial surface of the neui-al lamina is deeply and irregularly excavated, and another 



