PIGEON. 35 



SKULL. 



The various bones that compose the skull are fused together 

 in the adult pigeon, the sutures all being obliterated. 



At the back and under part is a round foramen — the foramen 

 magnum — which gives passage to the termination of the spinal 

 cord. At its posterior part is a single rounded condyle---the ' 

 occipital condyle— by which the skull articulates with the. atlas 

 of the spinal column. 



The nasal apertures are situated far back, near the base of the 

 beak. 



THE ORBITAL CAVITIES . 



Are large, and, placed laterally, and encroach upon the anterior 

 wall of the cranium — the septum separating the two being very 

 thin and delicate, and more or less incomplete. The roof of the 

 orbit is formed from before backwards by the frontal, prefrontal, 

 and lachrymal ; and the hind wall by the frontal, alisphenoid, and 

 basisphenoid. The brain case is arched and spacious. The 

 beak is chiefly formed of the premaxillse, which are triradiate 

 bones of large size, and which give off three processes : a frontal 

 process, which ascends to the frontal ; one placed along the middle 

 of the palate— the palatine process— to the palatine bones ; and 

 an external maxillary process, which composes the greater part 

 of the side of the beak, and unites with the maxilla. The two 

 bones are very early anchylosed, and form a single coalesced bone, 

 which is sometimes known under the name of the intermaxillary. 



THE MAXILLA 



Is a slender bone, expanded in front into the notch between the 

 palatine and maxillary processes of the premaxilla, being united . 

 also to the nasal and vomer. Posteriorly it is bifurcated where 

 it joins the jugal and palatine. 



THE PALATINES 



Are long slender bones. Anteriorly they pass under the maxiUo 

 palatines, and unite with the premaxillse — they join behind with 

 the pterygoids. Posteriorly the palatines converge toward 

 the rostrum of the basisphenoid, and are united to it by an 

 articular surface, which permits of a sliding movement of the 

 palatines upon the basisphenoidal rostrum. The pterygoids are 

 straight and slender bones. Their anterior or inner ends con- 

 verge and meet, while their posterior or outer end presents 

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