72 



LAND MAMMALS IN THE WESTERN HEMISPHERE 



anterior and concave posterior face, which in long-necked ani- 

 mals form regular "ball and socket" joints ; neural spines are 

 frequently wanting and, when present, are almost 

 always short and slender ; the zygapophyses are 

 very prominent and are carried on projections 

 which extend before and behind the neural arch ; 

 Fig 13 —Fifth ^^^ traiisverse processes are long, thin plates and, 

 cervical verte- exccpt in the scvcnth cervical, are usually pierced 

 side, ir., trans- by the caual for the vertebral artery, but in a 

 verse process, fg^ forms {e.Q. the camcls) this canal pierces the 



v.a"., posterior 



opening of ncural arch. 



canal for the ^2) 'pj-^g dorsal or thoracic vertebrae have more 



vertebral ar- 

 tery, pr.z. and OT Icss Cylindrical centra, with nearly flat faces, 

 pt.z., anterior ^^^^ ^^ ^j^^ centra, for the most part at their ends, 



and posterior ' '■ 



zygapophyses. are the concave facets for the rib-heads. The 

 spine "^^'^^ transverse processes are short and rod-like and 

 most of them articulate with the tubercles of the 

 ribs. The zygapophyses are smaller than in the cervical regiouy 

 less prominent and less oblique ; the anterior pair, on the front 

 of the neural arch, face upward and the posterior pair down- 

 ward. The neural spines are very much longer 

 than those of the neck and those of the anterior 

 dorsals are often of relatively enormous length, 

 diminishing toward the hinder part of the region. 

 (3) The lumbar vertebrae are almost always 

 heavier and larger than those of the dorsal region ; 

 they carry no ribs and their neural spines and 

 transverse processes are broad and plate-like and 

 the latter are far larger and more prominent than 

 those of the dorsals. As an especial degree of 

 strength is frequently called for in the loins, to- 

 gether with a greater flexibility than is needed 

 in the dorsal region, the modes of articulation 

 between the successive vertebrae are more com- 

 plex, sometimes, as in the Edentata, most elabo- 



-pr^. 



Fig. 14. — First 

 dorsal vertebra of 

 Wolf, left side, 

 c, centrum. ?•., 

 anterior rib- 

 facet. r"., pos- 

 terior rib-facet. 

 tr., transverse 

 process. pr.z. 

 pt.z., anterior and 

 posterior zyga- 

 pophyses. n.sp., 

 neural spine. 



