398 



ME. ST. GEOEGE MIVAET ON THE 



The ventral surface of the centrum agrees with that of the third vertebra, except that 

 the median hypapophysis is much less developed (fig. 20, hy), being only in the form 

 of a slight ridge extending antero-posteriorly along the middle third of the centrum. 



FOUETH VEETEBEA (natural size). 



Fig. 20. 



Fig. 23. 



Aspects. 



Fig. 20, lateral ; 21, preaxial ; 22, postaxial ; 23, dorsal ; 24, rentral. 



Letters as before, except that p denotes parapophysis, and jjs the rib-Uke, freely projecting, plenrapophysial 

 process. 



It also differs from the third vertebra in that its most postaxial part is decidedly, 

 though slightly, concave transversely, and in that the parapophyses, project a little 

 more sharply and strongly ventrad. 



The neural arch is very like that of the third vertebra, except that its pleurapo- 

 physial part is more developed, while its neurapophysis, being actually about the same 

 size, is relatively less. 



The plenrapophysial band is rather more extended antero-posteriorly, though it does 

 not quite attain the postzygapophysis as it does in the third vertebra ; while from the 

 ventral end of its postaxial margin (?'. e. from tlie parapophysis) a long, tapering, 

 styliform, rib-like process projects in nearly a straight line postaxially (fig. 20, ps). 



