THE GANNET'S OSTEOLOGY 507 



bird's skeleton, and it would be interesting to see what 

 modifications of it exist in the embryo Gannet, whilst still 

 in a state of cartilage. It has been fully described by 

 Dr. Shufeldt, who remarks on its unique form {t.c, p. 297) ; 

 it is, however, not so dissimilar from that of the Cormorant 

 as might be expected. A Gannet's sternum is of consider- 

 able length and very strong, the posterior portion forming 

 a complete and admirable shield to the abdominal parts of 



N.A. — NARIAL APERTURE LYING WITHIN THE RHINOTHECAL 

 GROOVE. 



RH. G. — RHINOTHECAL GROOVE. 



the body. Yet this shield exists, but in a less degree, 

 in the Cormorant, which does not plunge. 



As remarked by Mr. Pycraft, the carina or median ridge, 

 generally called the keel, affords in most species an indi- 

 cation of the bird's volant powers, for to the sides of the 

 keel, and to the body of the sternum, are attached the 

 muf^cles which raise and depress the wings. 



