292 OSTEOLOGY OP 1 TUBINARES AND STEGANOPODES. 



with the horizontal and fused palatine bodies behind. This latter por- 

 tion shows a small median carination just in front of the united heads, 

 and the postero external angles are rather sharp, being pointed directly 

 backward. 



Anteriorly, the pterygoidal heads meet each other and the fused 

 palatines, the three forming a groove on their upper sides for the ros- 

 trum. At their outer ends each pterygoid oilers a shallow cup to form 

 the usual articulation with the quadrate of the corresponding side. 



Professor Parker found that "in JSula alba the basi-temporals are as 

 little developed as in the Dromceidce, less than in any other carinate 

 bird. Behind each moiety there is a large oval opening, not far in front 

 of the occipital condyle; this exposes the loose diploe within. The small 

 Eustachian tubes open at a little distance from each other, in a wide, 

 shallow fossa, on the part where the three elements of the parasphenoid 

 meet." The description of these details agrees with the skull of the 

 specimen before us. Professor Parker, however, was fortunate in hav- 

 ing the skeleton of the ear parts in his specimen, and of them he says 

 that " in Sula alba the columella auris is very long and bent. It has a 

 small, cartilaginous, extra supra- stapedial process and a long attenuated 

 stylohyal." 



On either side, the entrance to the middle ear in this Gannet, as in 

 others of the same genus, is shallow, and it is situated quite internal 

 to the quadrate bone, while immediately mesiad to it there is a pit of 

 great depth, with its aperture looking downwards, and its base in the 

 vault of the cranium, wdiich seems designed for muscular lodgement; 

 the positions of the usual foramina about it are peculiar, and extremely 

 interesting in these birds. 



The bony wings that shield the entrance to the ears are large and 

 tdted up behind. Each one shows the double facet for the mastoidal 

 head of quadrate, the outer one having its inner margin encroached 

 upon by the pit described above. 



The posterointernal angle of either of these wings is connected with 

 the side of the elevated basi- temporal region by a bony bar. This con- 

 dition can best be seen from a posterior view. When speaking of the 

 orbital cavity I neglected to mention that the upper part of the septum 

 is longitudinally marked, as in most birds, by an open, single groove 

 for the passage of the olfactory nerve to the rhiual space beyond. The 

 exit for it from the brain-case is very small, indeed, and ou one side the 

 bone spreads over it, rendering the nerve track, for a fraction of the 

 initial part of its course, tubular. 



The brain-box itself is capacious and notable for its great width over 

 its compression in the vertical direction. Its anterior wall looks directly 

 downward and forward, making an angle of about 45 degrees with the 

 horizontal palatine bodies. Seen from behind (Fig. 27), the skull shows 

 above the extent to which the crotaphyte fossaa approach each other in 

 the utediau line and the crest that divides them from the occipital area, 



