334 CLASS XVI. 



sphenoid there pass obliquely backwards and outwards the so-named 

 ossa omo'idea of H^RISSANT. They are longitudinal, stile-shaped or 

 flat bones, which with their broader anterior extremity lie towards 

 the palate bones and are connected with them by articulation, whilst 

 the posterior extremity is connected moveably with an articular sur- 

 face on the inner margin of the quadrate bone close to its inferior 

 extremity. These bones are the ossa pterygo'idea or inferior wings 

 of the sphenoid and correspond to the ossa pterygo'idea interna 

 of fishes and reptiles. The quadrate bone of birds is large and 

 divided above into two arms ; of these the innermost mounts upwards 

 towards the orbit and terminates freely, the outermost is connected 

 by articulation with the temporal bone; below the quadrate bone 

 is connected with the articular cavity of the lower jaw by an elon- 

 gated articular surface, which runs obliquely inward and forward. 

 By means of the pterygoid bones the motion of the quadrate bones 

 is communicated to those of the palate and also to the upper jaw; 

 when the under jaw descends the quadrate bone is pushed forwards 

 and the upper jaw lifted up ; when, on the contrary, the mouth is 

 closed, the quadrate bone during the raising of the lower jaw is 

 drawn backwards and the upper jaw downwards. To this also 

 the malar bone contributes, which, elongated and stiliform, extends 

 downwards along the margin of the lower jaw, and is connected by 

 a part that always remains distinct (os quadrato-jugale] to an arti- 

 cular surface which the quadrate bone presents on its inferior 

 extremity. The intermaxillary bones are thin and flexible above, 

 in front of the frontal bones; in some birds the flexion occurs 

 lower, more towards the end or at the middle of the upper jaw 1 . 

 The greater part of the upper jaw is formed by the single intermaxil- 

 lary bone, of which the ascending portions (processus nasales) lie close 

 together between the nasal apertures and are connected with the 

 frontal bone. On the outside of these bones the nasal bones are 

 situated, and more behind and externally on the anterior margin 



1 Compare HERISSANT Observations anat. sur les mouvements du bee des Oiseaux, 

 Mem. de I'Acad. royale des Sc. de Paris, 1748, pp. 345 386, with figures; Cuv. Lep. 

 d' Anat. comp. u. p. 589, iv. pp. 99 113; and especially NITZSCH in MECKEL'S Archiv 

 f. Physiol. ii. s. 361379, s. 470, m. s. 384388. 



On the bony head of birds compare GEOFFROY ST.-HILAIBB Ann. du Mus. x. 1807, 

 pp. 342 360, PI. 27 (without adopting all the definitions of the bones, some of which 

 are quite wrong), MECKEL'S Syst. d. vergl. Anat. n. 2, s. 155 237, &c. 



