30 



TEETIAET VEETEBKATA OP THE PATtTM. 



deeper, while the oval capitular facets (c./.) are higher up and partly borne on the 

 base of the arch, the anterior being somewhat lower than the posterior. The 

 transverse processes are larger and more massive, and each bears a well-marked 

 tubercular facet {t.f.) on its outer end. The neural spine is very high and broad ; it 

 slopes strongly backwards, and its anterior face is convex from side to side, while 

 its posterior is deeply concave. The anterior border of the neural arch is deeply 

 concave from side to side, so that in a dorsal view of the vertebra much of the neural 

 surface of the centrum is exposed. At the same time the arch overhangs the 

 posterior border of the centrum to a great extent. The anterior zygapophyses (a.z.) 

 are mere shelf-like surfaces on the anterior border of the arch, and the posterior 

 zygapophyses [p.z.) form facets on the lower surface of the posterior border. 



In the posterior thoracic (text-fig. 13) the spine {n.sp.) is a low and backwardly- 

 directed crest, and, as in the middle region, the anterior border of the arch is very 



Text-f]g. 13. 



Posterior thoracic vertebra of ArsinoitJierium zitteli : A, from front ; B, from right side. 

 Lettering as in text-fig. 11. | nat. size. 



concave, while the posterior border overhangs to a corresponding extent. The 

 anterior zygapophyses (a.z.) are now concave from side to side, and external to them 

 there are prominent metapophyses connected by a ridge with the stout, somewhat 

 backwardly-directed, transverse processes. The outer ends of the transverse processes 

 bear small tubercular facets (t.f.). The posterior zygapophyses (p.z.) are prominent 

 and convex from side to side. The capitular facets (c.f.) are nearly circular and 

 are borne on short processes rising from the side of the neural arch above the 

 level of the neural surface of the centrum. 



Still further back the centrum is deeper in proportion to its width, and the 

 transverse processes are more prominent and less massive, while the neural arch 

 is still lower. 



In the lumbar region the vertebrae become much depressed, till in the hinder 



