PLATE IV. 



Fig. 1 . The atlas, upper view. 



Fig. 2. The atlas, under view. 



Fig. 3. The atlas, back view. 



Fig. 4. The atlas, side view. 



Fig. 5. The seven cervical and first dorsal vertebrae, upper view. 



Fig. 6. The seventh cervical vertebra, back view. 



Fig. 7- The seventh cervical vertebra, side view. 



One-fourth natural size; c, centrum; n, neurapophysis ; n.v, neural spine ; 

 d, diapophysis, da-dr, of the third to the seventh cervicals inclusive; 

 pi, pleurapophysis ; pi', (fig. 7) articular surface for head of first dorsal 

 rib; m, metapophysis ; nz (fig. 2), anterior articular surface ; z', posterior 

 zygapophysis ; hy, hypapophysis ; o, (figs. 1 & 3) its articular surface for 

 the odontoid or true body of the atlas ; r, division of the foramen alare 

 posterius, for the passage of the posterior branch of the occipital artery; 

 s, division of the same foramen for the passage of a branch of the second 

 spinal nerve; v, foramen alare anterius, communicating with q the canal 

 for the vertebral artery. 



