464 MANUAL OF ZOOLOGY SECT. 



farina sterni (car.\ formed, in the young Bird, from a separate 

 centre of ossification. The posterior border of the sternum 

 presents two pairs of notches, covered, in the recent state, 

 by ligament ; its anterior edge bears a pair of deep grooves 

 for the articulation of the coracoids. 



The skull (Fig. 263) is distinguished at once by its 

 rounded brain-case, immense orbits, and long pointed beak. 

 The foramen magnum (/. ;//.) looks downwards as well as 

 backwards, so as to be visible in a ventral view, and on its 

 anterior margin is a single, small, rounded, occipital condyle 

 (o. c.). Most of the bones, both of the cranial and facial 

 regions, are firmly ankylosed in the adult, and can be made 

 out only in the young Bird. 



The premaxillae (p.mx.\ are united into a large triradiate 

 bone which forms practically the whole of the upper beak. 

 The maxillae (mx.\ on the other hand, are small, and have 

 their anterior ends produced inwards into spongy maxillo- 

 palatine processes (mx.p.). The slender posterior end of the 

 maxilla is continued backwards by an equally slender 

 jugal (/.), and quadrato-jugal to the quadrate. The latter 

 (yu.) is a stout three-rayed bone articulating by two facets 

 with the roof of the tympanic cavity, and presenting below 

 a condyle for articulation with the mandible : the mandible 

 of the young Bird consists of a cartilage bone, the articular 

 (ar.\ and four membrane bones, which all coalesce in the 

 adult. The hyoid apparatus is of characteristic form, having 

 an arrow-shaped body with a short pair of anterior cornua 

 derived from the hyoid arch, and a long pair of posterior 

 cornua from the first branchial. The columeUa is a rod- 

 shaped bone ankylosed to the stapes, and bearing at its 

 outer end a three-aryed cartilage, or extra-columella, fixed 

 to the tympanic membrane. 



The shoulder-girdle (Fig. 260) is quite unlike that of 



