420 ME. ST. GEOEGE MIVAET ON THE 



THE LUMBO-SACRO-CAUDAL VERTEBRA. 



These vertebrse are normally twenty in number, and are, in the adult, anchylosed 

 together and also with the innominate bones into one great osseous mass (figs. 70-73). 



The various individual vertebrae cannot, therefore, be described from the adult ; but 

 the Museum of the College of Surgeons fortunately possesses a preparation of the sacral 

 vertebrae (figs. 58, 59, 60, 61, & 62) of a young Ostrich in an unanchylosed condition, 

 which enables the serial description of individual vertebrae to be completed. 



THE DORSO-LUMBAR VERTEBRA. 



The Twenty-sixth Vertebra. 



This vertebra has, of course, its preaxial surface formed to correspond with the post- 

 axial surface of the twenty-fifth vertebra. It may be greatly or not quite completely 

 overlapped by the iliac bones. 



Its parapophysis is smaller than that of the preceding vertebra, with a smaller 

 articular surface for the capitulum. 



Its diapopkysis is shorter, more compressed in an oblique pre- and postaxial direction, 

 so as to have its dorso-ventral diameter widest ventrad and preaxiad ; its articular sur- 

 face is also elongated in the same direction. 



Its spinous process is yet higher than in the twenty-fifth vertebra. 



This vertebra is mostly, but not always, confluent with the sacrum in the adult. It 

 supports a distinct rib (the ninth), which, however, generally ends freely at its ventral 

 extremity without joining any sternal rib ; indeed there is no true sternal rib corre- 

 sponding to it, though it may be connected by a styliform bone with the sternal rib of 

 the preceding vertebra. 



The Twenty-seventh Vertebra. 



This vertebra is always, in the adult, confluent with the sacrum ; and its rib (the tenth) is 

 almost always an anchylosed process (but not always so, as e. g. in the specimen 1362 b). 



Its spine is again higher. 



Its diapopkysis is still more compressed, appearing as a lamella, the greatest breadth 

 of which is inclined still more preaxiad and ventrad than in the twenty-sixth vertebra. 



The parapophysis is much smaller, and is directed as much dorsad as ventrad, if not 

 more so. 



The anchylosis of the transverse processes and rib results in the formation of a per- 

 forated transverse process, with its greatly produced extremity (the shaft of the rib) 

 extending ventrally, slightly arched convex preaxially, greatly flattened from within 

 outwards, and with sharp, pre- and postaxial margins (figs. 70, 71, 72, & 73, pi). 



