XII 



PHYLUM CHORDATA 



467 



b.hy 



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

 for the articulation of the coracoids. 



The skull (Fig. 279) is distinguished at once by its 

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

 The foramen magnum (/. m) 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 premaxillas (Fig. 279, /. mx) are united into a large 

 triradiate bone which forms 

 practically the whole of the 

 upper beak. The maxillae 

 (Fig. 279, mx), on the other 

 hand, are small, and have 

 their anterior ends produced 

 inwards into spongy maxillo- 

 palatine processes (Fig. 279, 

 mx.p). The slender poste- 

 rior end of the maxilla is 

 continued backwards by an 

 equally slender jugal (ju) 

 and quadrato - jugal to the 

 quadrate. The latter (Fig. 

 279, qu) is a stout three- 

 rayed bone articulating by FIG. 280 Columbia livia. Hyoid ap- 



r i L r paratus. The cartilaginous parts are 



tWO facets With the rOOf dotted. J.Ar./.basi-branchials; b hy, 



r .1 . j basi-hyal ; c . br, cerato - branchial ; 



of the tympanic cavity, and c , h j hyo id comu; */. br, ep i- 

 presenting below a condyle 



for articulation with the mandible : the mandible of the 

 young bird consists of a cartilage bone, the articular (Fig. 

 279, ar), and four membrane bones, which all coalesce in the 



b.br.3. 



