266 



1378. The first free vertebral rib of an Ostrich, right side. Hunterian. 



1379. The second rib of an Ostrich, right side. Hunterian. 



1380. The fourth rib of an Ostrich, right side. Hunterian. 



1381. The fifth rib of an Ostrich, right side. Hunterian. 



1382. The seventh rib of an Ostrich, right side. Hunterian. 



1383. The ninth rib of an Ostrich, right side. Hunterian. 



1384. The ninth rib of an Ostrich, left side. Hunterian. 



1385. The sacral and caudal vertebrae of a young Ostrich. 



The neural arch of the fifth sacral vertebra has advanced and rests over the interspace 

 between its own and the preceding centrum : at the eleventh vertebra it has resumed its nor- 

 mal position and connections. The pleurapophyses of the fifth to the eleventh sacral verte- 

 brse inclusive have undergone a corresponding change of position, and are articulated by an 

 expanded head, by synchondrosis, to a rough flat surface formed by the base of the neur- 

 apophysis and by a portion of their own and of the preceding centrum ; some have been 

 detached to show this articular surface : those of the tenth, eleventh and twelfth sacral ver- 

 tebrae remain ; their distal extremities expand and coalesce, forming a broad abutment applied 

 to the iliac bones. The diapophyses are directed upwards and outwards against the same 

 part, and are of considerable length, especially in the ninth to the fifteenth sacral vertebra:. 

 The spines of all the vertebrae are very lofty, compressed laterally, and already confluent with 

 each other at the middle of the sacrum. The dilated part of the neural canal is formed by 

 the increased breadth and flatness of the centrums, and by the wide expanse of the. neural 

 arches at the middle of the sacrum. In the seventh to the ninth of these arches there is a 

 wide aperture in each between the diapophysis and the base of the spine. The outlets for 

 the nerves are single and at the interspace of the neural arches, but those at the middle of 

 the canal show two grooves for the separate exit of the motor and sensory roots. In the 

 caudal vertebree the under part and sides of the centrum show deep longitudinal excavations 

 and pneumatic foramina, resembling the vertebrse of certain fishes ; parapophyses as well as 

 diapophyses are developed from most of the terminal vertebrae in this specimen. 



Presented by Prof. Owen, F.R.8. 



