THE ANATOMY OF BIRDS. — OSTEOLOGY. 



165 



smooth facet with which the pterygoid artic- 



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

 on each side a hasipterygoid process {ap) 

 ulates. These processes may be very 

 strong, and far back on the basisphenoid 

 body, when the pterygoids articulate with 

 them near their own posterior ends, as 

 in the struthious birds and tinamous (fig. 

 75, htp) ; 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 forvA'ard, 

 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 pait may be eth- 

 moidal, or basisphenoidal, or parasphe- 

 noidal thickening, pterygo-faceting, etc., 

 tliis '* 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 l)ase of the beak, where it widens 

 into the main body of the bone, may 

 commonly be seen, coming from between 

 tlie sphenoidal body and the lip of the 

 basitemporal underflooring, the orifices 

 of the eustachian tubes, and often also 

 the anterior ends of the carotid canal. 



Fig. 

 Parker, 

 nasal; n 



71. — Ripe oliii'k's skull, in iirofile, x 3 diameters ; after 

 px, premaxillary ; aln, ali-nasal cartilage; en, septo- 

 , nasal bone; /, lacrymal; pe, perpendicular plate of 

 ethmoid, as in fig. 70; ps, presphenoidal region; ns, alisplie- 

 noid ; /, frontal ; p, parietal ; ^q, squamosal ; so, superoccipital ; 

 eo, exoccipital ; oc, occipital condyle ; st. the cross-like object, 

 the stapes, whose foot fits fenestra ovalis, see fig. 83; q. quad- 

 rate; pd, pterygoid; qj, quadrato-jugal; ./, jugal; pa, palatine; 

 mx, ma.\illary. In the mandible: d, dentary; su, surangular; 

 a, angular; ar, articular; iap, internal angular process ; jmp, 

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

 foramen here, comes out of the ear, it for inferior 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 lias run in the carotid canal. The extent of the alisphcnoids (figs. 70, 71, as) can- 

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

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

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

 mina (any figs., 2) ; alisphenoid should not extend in fnmt 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 transmissi(m of the inferior divisions of the fifth (trigeminal 

 or trifacial) nerve. Tliis is the foramen ovale (any figs., 5) ; it is either in the alisphenoid, or 

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

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



