320 PKOF. ST. GEOKGE MIVAET ON THE 



lateral position, and sometimes in the smaller size, of the postcatapophysial subcentral 

 foramen of each side (fig. 8, f). 



Metapophyses and hyperapophyses are rather more marked; the proezygapophyses 

 look rather more preaxiad ; and the postzygapophyses look slightly more externad. 



The postaxial part of the centrum extends more ventrad than in the fifth vertebra, 

 so that, when laterally viewed, the vertebra appears bent ventrad postaxially. 



The SEVENTH VERTEBRA about equals the sixth in size. Unlike that of Struthio, it 

 does not differ from its serial predecessor as to the preaxiad development of the praezy- 

 gapophyses, since these extend preaxially beyond the centrum and parapophyses as 

 much as they do in the sixth vertebra, and the postzygapophyses project postaxially 

 beyond the centrum much more than in the sixth vertebra. It also differs from the 

 seventh vertebra of Dromaus, as well as from that of Stmthio, in that the rib-like 

 process is very much shorter, and the lateral vertebral canal is much less capacious dif- 

 ferences which all obtain in the preceding vertebrae (Plate LV. figs. 9-12). 



The postaxial ends of the laminae bounding the antero-posterior subcentral groove 

 are more or less marked as processes. 



Compared with the sixth vertebra, the seventh one has a rather more prominent 

 neural spine ; and this is confined to the antero-posterior middle third of the neural arch. , 

 It has also more marked catapophyses and a deeper subcentral groove. The postzyga- 

 pophyses are longer and look more externad. The hyperapophyses are smaller and 

 have advanced more preaxiad of the postaxial ends of the postzygapophyses. 



There is a marked and sudden difference from the foregoing vertebrae in the appear- 

 ance (when the vertebra is viewed dorsally) of a deeply concave postaxial margin of the 

 neural arch. The pleurapophysial lamella is antero-posteriorly shorter ; and thus the 

 subcentral oval foramen of each side, leading into the vertebral-artery canal, appears 

 close behind its postaxial margin, and can be seen when the vertebra is viewed laterally 

 (fig. 9,y'). There is no free rib-like process, or but a rudimentary one. The postaxial 

 surface of the centrum looks almost entirely postaxiad, and very little dorsad. 



The ventral margin of the postaxial surface of the centrum is more deeply notched 

 than heretofore. 



Viewed laterally this vertebra is seen to be bent ventrad postaxially, as is the sixth 

 vertebra ; but the more antero-posteriorly continuous development of the catapophysial 

 ridges makes this less evident. 



When this vertebra is viewed ventrally we see at the preaxial part of each catapo- 

 physial ridge two small antero-posterior grooves, the inner one of which (fig. 11, c, g) 

 might be taken as corresponding with the apparently similar grooves of the sixth 

 vertebra. Eeally, however, it is the outer groove (g) which does so, while the inner 

 groove is very different, not being bordered externally (as in the sixth vertebra) by the 

 parapophysis, but by the preaxial end of the catapophysial ridge, while it is bounded 

 medianly by a prominence which has no place in the sixth vertebra, but which is in 



