AVES. 



117 



bone presenting a very large central process posteriorly, the central xipheid 

 process (lophosteon), outside which is a large bifurcated process (metosteon), the 

 two projections of which are called the median and external xiphoid processes, 

 and antero-laterally is the ridge (pleurosteon), which gives attachment to the 

 ribs. The inferior edge of the central ridge is called the carina; often a 

 small median spine exists anteriorly, the rostrum or presternum. 



The following Table shows the ntimber of vertebral segments usually found- 

 in domesticated birds : — 



Rasores, 



Natatores, 



Dorsal. "t^umbo-Sacral. Coccygeal. 



i ' \ 



The costal cartilages are ossified, and thus birds are said to possess sternal 

 and vertebral ribs. Some of the lumbar and coccygeal vertebrae become 

 anchylosed, and assist in forming the sacrum; it is not indeed easy to define 

 the exact points of demarcation between the lumbar, sacral, and coccygeal 

 regions. The coccygeal bones terminate in an expanded segment, termed the 



Fig. 3S. 

 Skull of & fowl. "A, Inferior aspect, the mandible being removed ; B, Lateral aspect ; 

 px, Premaxilla; mx, Superior maxilla; p. Palatine bone; v, Vomer; j, Jugal bone; 

 qj, Quadrato-jugal bone; I, Lachrymal; me. Median. ethn?oid ;/, Frontal ; pf, Post-fronta) 

 process ip, Parietal ; pt. Pterygoid ; q, Os quadratum ; S2, Squamosal ; eu, Process before the 

 Eustactdan aperture ; ho, Basi-occipital, and so, Supra-occipital bones ; ar, Articular, 

 a, Surangular, and d, Dentary portion of the Mandible. 



ploughshare bone. In the skull we have to note chiefly the absence of teeth^ 

 the existence of only one occipital condyle, and the articulation of the man- 

 dible or lower jaw, which does not articulate directly with the skull above,, 

 but there is interposed the quadrate bene, which, when the lower jaw is; 

 depressed, acts on a process, the quadrato-jugal bone, connecting it with the 

 maxilla, and so simultaneously raises the upper jaw, there being usually cl^Thti 

 vertical motion between the latter and the cranium. 



