Tl^RTIAliY VEliTEIJRATA OF THE FAYCM. 
;]0 
<lce])er, while the oval capitular facets {c.f.) are higher up and partly borne on the 
base of tlie arch, the anterior being somewhat lower than the ])osterior. The 
transverse ])rocesses 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 
slo])es 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 
})osterior 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-hg. 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-fig. ]3. 
A x4 B X i 
Posterior thoracic vertebra of Arsinoitheriuni zitteli : A, from front ; ]}, 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 witli the stout, somewluit 
backwardly-directed, transverse processes. The outer ends of the transverse processes 
l)ear small tubercular facets (t.f.)- The posterior zygapophyses (p.z.) are prominent 
and convex from side to side. T'he capitular facets (c.f.) are nearly circular and 
are borne on short processes rising from the side of the neural arch above tlie 
level of the neural surface of the centrum. 
Still further back the centrum is deeper in ])roportion to its width, ami tlie 
transverse processes are more prominent and less massive, while the neural arch 
is still lower. 
in the lumbar region the vertebrie become much depressed, till in the hinder 
