THE PIGEON. 195 



60. The quadrate (gu\ a short, stout, irregular bone, 

 articulating by a double head with two facets in the dorsal 

 region of the tympanic cavity, the upper of the two facets 

 being furnished by the squamosal, the lower by the prooric : 

 from its articulation, the quadrate takes a direction down- 

 wards and forwards ; its inner border sends off a large 

 pointed ascending process directed upwards, inwards, 

 and forwards, while its distal end forms a transverse cylin- 

 droidal articular surface or condyle for the mandible. 



t6i. The columella (Fig. 48), a small and delicate rod 

 bone, having its expanded inner end fixed in the fenestra 

 i 



s.st. 



l^k 



e.st. 



i.st. 



FIG. 48. Columba livia. The columella auris ( x 8). 

 The cartilaginous parts are dotted. 

 e.st, extra-stapedial : i.st, infra-stapedial : s.st, supra-stapedial : st, 

 stapes. 



ovalis, a small aperture in the inner wall of the tympanic 

 cavity, while its cartilaginous outer end is fixed, in the entire 

 head, to the inner surface of the tympanic membrane (see 

 317, p. 250.) 



The columella consists of a slender bony rod, having at its inner end 

 an oval plate of bone, the stapes (st), and at its outer end a tri-radiate 

 cartilage : the central division of the latter, forming the direct con- 

 tinuation of the stapedial rod, is the extra-stapedial; the second 

 division, situated dorsally, is the supra-stapedial (s.st) ; the third, 

 central in position, the infra-stapedial (i.st) ; the supra- is connected 

 with the extra-stapedial by an oblique bar of cartilage. 



62. The ptery golds (Fig. 47, //), short, stout, paired 

 bones on the base of the skull, each articulating behind 



o 2 



