PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



77 



project nearly as much as do those of the dorsal region, notwithstanding the 

 smaller size of the vertebrae. Like the centra, they evidently permitted not only 

 extensive vertical flexion, but a considerable lateral one as well. 



The axis has a rather narrow spine, not expanded anteroposteriorly above, 

 and it is but little longer than the height of the centrum. It is thin in front, much 

 thickened and rugose behind, and is directed obliquely forward. The precise 

 length of the spine of the next following vertebra can not be determined. It is 

 flattened at its base, cylindrical, slender, and evidently pointed above; its extremity 

 is directed forward at an angle of about 45 degrees with the long axis of the centrum. 

 The spine of the fourth vertebra could not be connected with its centrum, and 

 its length is, consequently, unknown. That of the fifth vertebra is complete, or 



Fig. 48. — Edaphosaurus navomexicanus, X yi. A, vertebrae as numbered, No. 674, University of 

 Chicago; B, rib of eighth or ninth vertebra. 



practically so. It is directed upward and forward at a little less angle than the 

 preceding ones; it is gently curved below, nearly straight above, and is obtusely 

 pointed at its extremity. It is oval in cross-section above its flattened and rugose 

 base, and has no lateral tubercles. The next spine is stouter, but is preserved only 

 as far as the extremity of the one preceding it, with which it lay in close matrical 

 contact above; it must have been at least 3 inches longer than that spine. It has 

 two or three tubercles on its sides, in the form of rounded protuberances, pro- 

 jecting about a fourth of an inch. The sixth spine is still stouter, but only about 

 5 inches of it can be connected with the centrum. It is directed less obliquely 

 forward, and the single pair of tubercles that this portion bears are larger. On the 

 tenth, the base of the spine, about 3 inches in length, was recovered; it is directed 



