THE ANATOMY OF BIBBS. — OSTEOLOGY. 



159 



thickened by the underflooring of the parasphenoid (fig. 70, rbs). The rostrum often bears 

 on each side a basipterygoid process (up), — a smooth facet with which the pterygoid artic- 

 ulates. These processes may he very 

 strong, and far back op. the basisphenoid 

 body, when the pterygoids articulate with 

 them near their own posterior ends, as 

 in the struthious birds and tinamons (fig. 

 75, Mp) ; or they may be further along 

 on the rostrum, and the pterygoids then 

 articulate near or at their fore-ends. The 

 rostrum may be produced far forward, 

 beyond the maxillo-palatines and vomer 

 even, as in an ostrich ; or it may bear the 

 vomer at its end ; or may be embraced 

 by forks of the vomer ; the palatines may 

 glide along it, or be remote from it on 

 either side. In any event, whatever its 

 production, whatever part may be eth- 

 moidal, or basisphenoidal, or parasphe- 

 noidal thickening, pterygo-faceting, etc., 

 this " beak " of the basisphenoid is 

 always in the axis of the base of the 

 skull, and at the bottom of the inter- 

 orbital plate ; it may be horizontal, or 

 obliquely ascending forward; and the 

 variety of its relations with the pterygo- 

 palatine and vomerine mechanism fur 

 nishes important zoological characters, 

 as we shall see when we come to treat. 

 of palatal structure particularly. Just at 



the base of the beak, where it widens fig. 71. -Elpe chick's skull, in profile, x 3 diameters; after 



into the main body of the bone, may Parker, px, premaxillary ; atn, ali-nasal cartilage ; en, septo- 



11 . j> 1 J. nasal; n, nasal bone; t, lacrymal; ne, perpendicular plate of 



commonly be seen, coming from between ethmoid, as in fig. 70; p,, presph^noidal region; as, aUsphe- 



the sphenoidal body and the lip of the noid;/, frontal ;p, parietal; s$, squamosal; so, superoocipital; 



haai+Prnnnral imHprflnnrinff fhp nrifipps *°' e'^'^'Pital ; oc, occipital condyle; st, the cross-like object, 



Dasiteinporai unaemoonng, tne Onnces the stapes, whose foot fits fenestra ovalls, see flg. 83; g.quad- 



of the eustachian tubes, and often also rate; p^, pterygoid; 9j,quadrato-jugal;j,jugal; pa, palatine; 



the anterior ends of the carotid canal. '»^. °'«^il"«^y- In the mandible: d, dentary; m.surangular; 



a, angular; or, articular; tap, internal angular process; pop, 



If a bristle, passed into a questionable posterior angular process. 2, optic foramen ; 5, foramen ovale, 



foramen here, comes out of the ear, it forinferior divisions of the 5th nerve. (Compare fig. 70.) 



has gone through the eustachian tube : if it comes out below the ear, on the floor of the skull, 

 outside, it has run in the carotid canal. The extent of the alisphenoids (figs. 70, 71, as) can- 

 not be determined in old skulls. They lie at the back lower border of the orbital cavity, clos- 

 ing in most of the brain box that is not foreclosed by the frontal bone. You wUl always find 

 at the back of the orbit, close to the mid-line, and rather low down, the very large opUe fora- 

 mina (any figs., 2) ; alisphenoid should not extend in front of these orifices. A little below and 

 behind the optic foramina, and much more laterally, not far from the quadrate itself, is a con- 

 siderable foramen, quite (Constant, for transmission of the inferior divisions of the fifth (trigeminal 

 or trifaeial) nerve. This is the foramen ovale (any figs., 5) ; it is either m the alisphenoid, or 

 between that bone and the prootic ; it must not be mistaken for one of the several smaller holes, 

 usually seen close about the optic foramen, which' transmit the nerves (oculo-motor, pathetic. 



