1898.] 



OSTEOLOGY OF BlRlDS. 



87 



THe atlas vertebra of the Steganopodes has the odontoid ligament 

 ossified : the neural arch is very broad and flattened, and devoid of 

 a crest. The axis has a fossa immediately underlying the odontoid 

 process, into %yhich piieumatic foramina frequently open. The 

 remaining vertebrse in the different genera and species vary 

 greatly inter se, and do not seem to afford any characters which 

 can be regarded as peculiar to the group (see table, p. 99). 



In the sternum of the Steganopodes the carina is produced far 

 forwards beyond the corpus sterni\ it decreases in depth rapidly 

 from before backwards, terminating not far behind the middle of 

 the corpus sterni — save in PA«e</(0/i and F^Vf/ate. The acrocoracoid 

 bears a large facet for articulation with a corresponding facet on the 

 outer side of the dorsal extremity of the furculum. The furculum 

 articulates or is even ankylosed with the carina in Pelecanus and 

 Fregata. 



Fig. 1. 



Sternum of Fhaethon flavirostris, left side view (nat. size). The small outline 

 immediately to the right represents the form of the posterior border of 

 the sternum, ventral view. 



A., Acrocoracoid ; C, Carina ; A.l.p., Anterior lateral process ; Pip., Posterior 

 lateral process ; I.p., Intermediate process ; F., Furculum ; &, Scapular ; 

 M., Metasternum. 



In PhaetJion the carina is of the same form, but continued 

 backwards farther than in any other Steganopod save Fregata ; 

 dorsally the furculum does not "articulate with the acrocoracoid by 

 means of apposed flattened facets ; ventrally it articulates with 

 the anterior border of the sternum, and not with the extreme 

 antero-ventral angle as in the other forms. The anterior end of 



