AXTAL SKELETON OP THE STRUTHIONID^. 15 



This bone is narrower in proportion to its pre- and postaxial length than in Struthio. 

 The coracoid grooves are not nearly so approximated ; and their dorsal margins project 

 but little, if at all, preaxiad beyond their ventral margins. The costal angles are narrower 

 in proportion to their length. There is no median preaxial projection. The lateral 

 xiphoid processes are small, and project but little postaxiad, leaving but a moderate 

 notch (and no median xiphoid process) between them. The sides of the sternum are 

 less concave. The median ventral prominence (fig. 10,/) is not flattened. Each pleu- 

 rosteon has but three articular surfaces; and each of these has a deep excavation 

 postaxial to it. The ventral facet of each articular surface exceeds the dorsal one in 

 size ; but they are most nearly equal in the third articular surface. 



VERTEBRAL PARTS AND PROCESSES. 



The centra resemble generally those of Struthio, except as to which are the ones 

 which became ankylosed. These parts may all but abort altogether, as in the anterior 

 caudal vertebrae. 



The neural lamince do not show such signs of shifting as in the lumbar vertebrae of 

 Struthio. The neural arches may entirely abort, while the centra still exist in an im- 

 perfect manner, as in the anterior caudal vertebrae. The substance of the laminae may 

 be so cellular as to be most extremely imperfect in development, as in the lumbar and 

 sacral vertebrae. Diapophyses may be quite absent, if not blended with the spinous 

 processes, as in the last six presacral vertebrae. 



The neural spines are most expanded, pre- and postaxiaUy, in the dorsal vertebrae. 

 They may be laterally bifid, as in the thu-d cervico-dorsal vertebra. The zygapophyses 

 are developed as in Struthio ; and the metapophyses ofler no great differences. 



Hyperapophyses are only conspicuous in the second, third, fourth, and fifth vertebrae. 



Diapophyses and parapophyses are occasional!)' absent where they are present in 

 Struthio, notably in the last five lumbar vertebrae. No such processes abut against the 

 ischium. 



The pleurapophyses of the cervical region differ greatly from those of Struthio by 

 their shortness and non-styloid form. 



Hypapophyses are nowhere distinctly paired. 



Catapophyses are found preaxiad to the fifteenth vertebra. 



The vertebrae are raised above {i. e. dorsally to) the acetabula. 



The vertebral ribs have a different twist from that existing in Struthio. 



The uncinate processes do not seem to be more than three in number. 



