28 MEMOIRS OF THE CARNEGIE MUSEUM 



broken away over a portion of the posterior end of the centrum, reveahng the intra- 

 mural laminae. See PI. VI., and Fig. 3, PI. IV. 



The Fourth Dorsal. — Centrum short, with strongly convex anterior and shallow 

 concave posterior extremity. The latter is broadly expanded transversely and 

 vertically. Laterally and inferiorly there is a deep median constriction extending 

 into the pleuro-central cavities. These cavities are bisected by the short pleuro- 

 central laminae that support the large obovate capitular rib facets, which are borne 

 about equally by the centrum and neural arches, but extend into the pleuro-central 

 cavities. The neural arch is elevated. The transverse processes are widely expanded, 

 broadly rugose distally and superiorly, and bear at their extremities the tubercular 

 facets, which look more outward and less downward and backward than in the pre- 

 ceding vertebrse. Inferiorly the transverse process is supported by the inferior branch 

 of the anterior blade of the horizontal lamina and by the perpendicular inferior blade 

 of the diapophysial lamina, w^hile on its upper side there is a rudiment of the superior 

 blade of the latter lamina. Inferiorly the prezygapophyses are supported by a single 

 lamina on the right side and a double one on the left. These extend from the inferior 

 side of the zygapophyses to the superior surface of the capitular facet. The posterior 

 zygapophyses are continued into the diplosphenal articulation so characteristic of 

 the succeeding dorsals. These unite below to form a very sharp median lamina ex- 

 tending to the superior border of the neural canal. Posteriorly the transverse proc- 

 esses present broad, flat surfaces continuous with those of the posterior aspect of the 

 neural arch. The extremities of the transverse processes show^ a rather deep posterior 

 cavity overhung by the expanded superior rugosity. The paired spines are con- 

 fluent for some distance above the superior surface of the posterior zygapophyses. 

 They are styliform and present at their extremities rather elongated and expanded 

 external rugosities. The median spine is less pronounced than in the preceding 

 vertebra. 



The Fifth Dorsal. — Centrum opisthocoelous, extremities widely . expanded, deep 

 median constriction, a low median ventral keel, pleuro-central cavities deep, only 

 separated by a thin median lamina. Capitular facets obovate, very large, and borne 

 on sides of neural arch. Neural arch much extended vertically. Zygapophyses 

 not so broad as in preceding vertebrse, continued into the characteristic diplosphenal 

 articulations, which are supported below by a thin median lamina posteriorly, and 

 anteriorly by a much stronger but shorter lamina parallel with that which supports 

 the prezygapophyses and like it confluent with the capitular facet. Widely extended 

 and stout transverse processes, with broad, distal, superior rugosities, bearing at their 

 extremities the rather large triangular tubercular rib facets. The latter are sup- 



