406 



ME. ST. GEOEGE MIVAET ON THE 



As regards the centrum, its preaxial surface has the shape of its ventral margin 

 changed by the appearance of two small hypapophysial processes (fig. 36, hy). 



Its postascial surface is larger both actually and relatively ; while its ventral margin 

 has once more become more extended transversely than its dorsal margin, and at the 

 same time is less concave than in the vertebra last described (fig. 37, pc). 



The neural surface of tlie centrum may be more exposed by the further cutting 

 away, as it were, of the preaxial part of the neural arch. 



The ventral surface of the centrum presents somewhat of a return to the proportions 

 of the third vertebra, if abstraction is made of the hypapophyses (fig. 39). 



Fig. 35. 



SEVENTEENTH VERTEBEA (| nahiral size). 

 Fig. 36. 



Fig. 38. 



Fig. 39. 



Fig. 37. 



Aspects. 

 Fig. 35, lateral ; 36, preaxial ; 37, postaxial ; 38, dorsal ; and 39, ventral. Letters as before. 



These latter processes (which may conveniently be said to represent and take the 

 place of absent catapophyses) project as a pair of short processes, springing from 

 beneath about the middle (both antero-posteriorly and transversely) of the centrum. 

 They extend ventrally and preaxially, and diverge from each other towards their apices, 

 instead of converging like the catapophyses of the sixteenth vertebra. 



The hypapophyses may be separated by a notch which extends dorsad to the general 

 level of the ventral surface of the centrum, or may be only imperfectly divided from one 

 another as in the specimen figured. 



