20 



shortened, though still long and large in proportion to the neural arch. The met- 

 apophyses, m, m, stand out from the upper part of the side of the neural arch 

 behind the anterior zygapophyses, z. The diapophyses, d, d, are developed from the 

 base of the neural arch, which has descended lower upon the sides of the centrum ; 

 and now we find another element — the pleurapophysis, pi — restored to the segment, 

 but reduced to rudimental proportions and anchylosed at two points. Its vertebral 

 end is bifid ; one portion, answering to the head of the rib, has coalesced with the 

 side of the centrum (at p, fig. 5) ; the other, answering to the tubercle, has united 

 with the under part of the diapophysis, d: what may be termed the body of the rib 

 is a short but broad rhomboidal plate (fig. 6, pi), projecting outward, downward and 

 a little backward. The space intercepted between the pleurapophysis and diapophy- 

 sis forms the canal, v, for the vertebral artery. 



The fifth cervical (Plate I. Cs) differs from the sixth by its smaller dimensions, 

 especially by its shorter spine, and by the diminution in the breadth of the pleurapo- 

 physis, which terminates by a thick obtuse end : it sends out, however, a thin plate 

 forwards from its vertebral end. The metapophysis is a large obtuse tubercle, 

 Plate IV. fig. 5, m ». 



In the fourth and third cervicals (Plate V. figs. 3 & 4) the neural spine is still 

 more reduced, and, contracting from its base, assumes a triangular shape, fig. 4, ns. 

 The anterior zygapophyses, fig. 3, z, are concave transversely, and look upward and 

 inward ; the posterior ones, fig. 4, z', are convex, with the reverse aspect : the met- 

 apophysis, m, continues to be developed as a distinct tuberosity, external and posterior 

 to the prozygapophyses ; and the pleurapophysis continues to send forward the 

 pointed plate from its fore-part, fig. 4, pi, its outer end, pi, being thick and tuberous, 

 like the diapophysis, d, above. 



The dentata (Plate V. figs. 1 & 2) has its spine extended in the antero-posterior 

 direction, and of great strength, though low ; with a thick angular ridge projecting 

 from its fore-part and overhanging the neural canal; it is broad, flattened and 

 almost vertical behind, and has a subbifid summit (Plate IV. fig. 5, *, and Plate V. 

 fig. 1, ns). There are no metapophyses and no anterior zygapophyses, but the ana- 

 logous articular surfaces (figs. 41 & 42, zn) have descended upon the antero-lateral 

 parts of the coalesced centrum of the atlas or ' odontoid process,' and are adapted to 

 corresponding surfaces of the bases of the neural arch of the atlas. The posterior 

 zygapophyses, z', are wide apart, and are convex. The diapophysis, d, is short and 

 obtuse ; the pleurapophysis, pi, still developes its anterior angle, Plate V. fig. 2, pi 1 . 

 The fore-part of the odontoid process, o, is a rounded tuberosity, on the under sur- 

 face of which is the oval, slightly convex surface for articulating with the hypapo- 

 physis (Plate IV. fig. 3, o, hy), which has coalesced with the neural arch, ns, of the 

 atlas, and is commonly called the 'body of the atlas.' The under surface of the 

 centrum of the dentata developes a hypapophysial ridge. 



The atlas, viewed from behind, as in Plate IV. fig. 3, is a large, transversely ob- 



