STRUCTURE OF BIRDS. 



25 



by others held to be the malar bone. The palatal bones, 

 forming the roof of the mouth, are scarcely visible in this 

 view. The vomer separates the cavity of the nostrils, w, when 

 complete. 



Fig. 2 represents the cranium and upper 

 ^ jaw of the Raven, viewed from below. The 

 occipital bone, a, b, b, c, of which a is the 

 basilar or anterior portion ; 6, b, the two 

 lateral portions ; c, the posterior. The oc- 

 cipital foramen for the passage of the spinal 

 cord is seen, of a somewhat triangular form, 

 having on its anterior margin a small hemi- 

 spherical prominence for the articulation 

 of the first cervical vertebra. The temporal 

 bones, d, d. The tympanic bone, or os 

 quadratum, e, e. The basilar portion of the 

 sphenoid bone,/,* its pterygoid bones or 

 ossa quadrato-palatina, g, g ; and its large 

 orbital plates, h, h. The palate bones, i, i. 

 The malar bones, j, j. The os quadrato-maxillare, k, k, or 

 slender process of the upper maxillary bones, /, /. Lastly, the 

 intermaxillary bones, m, m, of which the superior part is seen 

 behind the aperture of the nares, ', 



Fig. 2. Cranium and Upper 

 Jaw of Raven. 



The lower jaw. Fig. 1, oc, n. 



originally composed of 



twelve pieces, which remain more or less disunited in many 

 of the waders and aquatic birds for a considerable time, is 

 here completely ossified. Its two thin, broad, erect sides, are 

 named the rami or branches, v ; the union of which anteriorly, 

 from w to the point, is named the symphysis, and determines 

 the outline of the lower horny mandible. Behind the middle 

 of the ramus, there is in many cases a vacuity, y, in others 

 two, and sometimes none. The part by which the articulation 

 is effected with the os quadratum, z, is the condyle, and is of 

 various forms, with several processes in its vicinity. 



The upper jaw preserves a degree of mobility in its union 

 with the cranium, which is effected by the medium of the 

 slender quadrato-maxillary bone. Fig. 1, t. Fig. 2, k, by which 

 the motion of the os quadratum, Fig. 1, c?, is communicated to 



