The second or =axis vertebra= also differs a good deal from the other cervicals. The centrum is massive, and is terminated in front by a very large slightly concave articulating surface formed by the =odontoid process= (fig. 41, 3) which is united with the centrum by suture only, and is really the detached centrum of the first vertebra. The cervical rib (fig. 41, 9) articulates with two little irregularities on the odontoid process. The posterior surface of the centrum is convex. The neural arch is strongly developed and terminated dorsally by a long neural spine (fig. 41, 5), its sides are notched, slightly in front and more prominently behind for the exit of the spinal nerves. It is drawn out in front into two little processes bearing a pair of upwardly and outwardly directed prezygapophyses, while the postzygapophyses are similar to those of the other cervical vertebrae. The last two cervical vertebrae resemble the succeeding thoracic vertebrae, in the increased length of the transverse processes, and the shifting dorsalwards of the facet with which the capitulum of the rib articulates. THE THORACIC VERTEBRAE. The thoracic vertebrae commence with the first of those that bears ribs reaching the sternum. They are ten in number, and the first eight are directly connected with the sternum by ribs. The =third= of them may be taken as a type. It has a thick cylindrical centrum, concave in front and convex behind, there is a slight hypapophysis, and the centrum is suturally united with a strong neural arch enclosing a narrow neural canal. The neural arch is drawn out dorsally into a wide truncated neural spine, and laterally into two prominent transverse processes, with the ends of which the tubercula of the ribs articulate, while the capitulum articulates in each case with a step-like facet (fig. 42, A, 3) on the anterior face of the transverse process. The prezygapophyses (fig. 42, A, 2) are borne on outgrowths from the bases of the transverse processes, and the postzygapophyses on outgrowths at the base of the neural spine. The thoracic vertebrae behind the third have no hypapophyses, and the capitular facets gradually come to be placed nearer and nearer the ends of the transverse processes, at the same time becoming less prominent; otherwise these vertebrae are just like the third. [Illustration FIG. 42. ANTERIOR VIEW OF A, A LATE THORACIC AND B, THE FIRST SACRAL VERTEBRA OF A YOUNG CROCODILE (_C. palustris_). × 1/3. 1. neural spine. 2. process bearing prezygapophysis. 3. facet for articulation with the capitulum of the rib. 4. sacral rib. 5. surface which is united with the ilium. 6. concave anterior face of centrum.] In the first and second thoracic vertebrae the capitulum of the rib articulates, not with a facet on the transverse process, but with a little elevation borne at the line of junction of the centrum and neural arch. THE LUMBAR VERTEBRAE.