AXIAL SKELETON OF THE OSTRICH. 449 



The centra may or may not develop parapophysial, catapophysial, or hypapophysial 

 processes. 



The pre- and postaxial diameter of centra may greatly exceed their transverse 

 dimension, as in the cervical vertebrae. 



The reverse condition may obtain, as in the thirty-first to thirty-seventh vertebrae. 



The ventral surface of the centrum may be much excavated antero-posteriorly, as in 

 the caudal vertebrae. 



Neural Lamince. 



The neural laminae are attached to their own centra only, except in the thirty-second 

 to the thirty-sixth vertebrae. 



In the thirty-second, thirty-third, and thirty-fourth vertebrae the neural arch rests on 

 part of the centrum of the adjacent preaxial vertebra; but the arch may, as in the 

 thirty-fii'st vertebra, partly rest on the centrum postaxial to its own. 



The neural arches are highest relatively to their transverse extent in the lumbar 

 vertebrae ; they are most pre- and postaxially developed in the cervical vertebrae, and 

 least so in the caudal vertebrae. 



Adjacent neural arches may join each other by suture, as in the lumbar and sacral 

 vertebrae in the young condition — by anchylosis, as in the sacral region of the adult — ^by 

 articular processes, as in most parts of the axial skeleton — or in none of these ways, as 

 in the caudal region. 



The neural laminae almost always develop diapophyses. 



Neural Spiiies. 



These parts attain their maximum height in the lumbar region, where (in the adult) 

 they unite together by anchylosis. 



They are most pre- and postaxially extended in the cervical region, and most trans- 

 versely extended, relatively, in the caudal region. 



A neural spine may be trifid, as in the eighth caudal. 



Prezygapophyses. 



These surfaces may be wanting when the postzygapophyses exist in the same vertebra, 

 as in the atlas ; they may be wanting as well as the postzygapophyses, as in the post- 

 dorsal vertebrae. 



Very much longer (pre- and postaxially) than broad, they may broaden considerably, 

 as in the dorsal vertebrae. 



Having become larger they may again diminish in size, as in the posterior dorsals. 



Strongly convex pre- and postaxially, as in the cervical region, they may become 

 nearly fiat, as in the dorsal region. 



VOL. VIII. — PART VII. March, 1874. 3 b 



