OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 381 



dorsal is shown in Fig. 4, P. In this vertebra the spine is more 

 elevated than it is farther back; in much probability the spine 

 is yet higher in the more anterior dorsals. The spine is thin, and 

 has no tubercular projections of any kind. Another rib-bearing 

 vertebra is shown in Fig. 4, N, with a less pronounced spine. The 

 posterior zygapophyses overhang the centrum at a considerable 

 elevation and there is, as in all, an excavation in the sides above. 

 The articular processes for the rib form two surfaces separated 

 by a distinct interval. The diapophysis is on the arch just back 

 of the anterior zygapophysis ; it projects but little or not at 

 all beyond the margin of the zygapophysis. The facet for the 

 capitulum is shown in several specimens as a small surface near 

 the front end of the centrum, high up; whether it is on the arch 

 or the centrum cannot be said, but it appears to be on the former. 

 A series of five lumbar vertebrae, in all probability a part of the 

 same skeleton as that to which the figured dorsals belong, differ 

 in their somewhat greater stoutness, and in the entire absence of 

 any diapophysial process or facet; the spine is also vestigial. One 

 of these vertebrae is shown in Fig. 4, 0. 



Sacrum (Fig. 4, K). — The two sacral vertebrae and a connected 

 lumbar were found in one specimen closely attached to the inner 

 side of the left ischium. The sacral ribs on one side have been 

 worked out fully, and on the other partly. The dorsal arch 

 unfortunately had been injured somewhat. The sacral ribs are 

 long, and those of the second vertebra very slender. They resemble 

 so closely those of some lizards that it is needless to describe 

 them further. As is seen, the first one has an expanded extremity 

 and bore nearly the whole support of the ilium; the posterior one 

 projects markedly forward. 



Caudals. — Numerous caudal vertebrae are preserved isolated. 

 One of a series of three proximal vertebrae is shown in Fig. 4, B, 

 from below. The co-ossified ribs or transverse processes are 

 elongate; none is preserved entire; they turn backward, as usual. 

 More posterior caudals have tubercles on the sides for the posterior 

 ribs. A yet more posterior caudal is shown in Fig. 4, H; it has a 

 slight, thin spine on the posterior half, scarcely rising above the 

 level of the zygapophyses. Three found attached in the clay matrix 



