280 OSTEOLOGY OF TUBIXARES AND STEGANOPODES. 



The pituitarj fossa is deep and its posterior wall entire. There seems 

 to be two carotid openings at its base, but they are very close together, 

 and I would not be surprised to find them united in one in some speci- 

 mens. The floor of this cranial cavity is a circular convexity, bounded 

 on the sides by the bony wall of the middle ear, in front by the broad 

 posterior wall of the pituitary fossa, while behind, after a low descent, 

 it opens out upon the flat upper surface of the occipital condyle. In 

 trout of the pituitary pit we find a considerable of a partition separating 

 the two distinct and circular optic foramina, each opening into an orbital 

 cavity. Above these there is a nearly horizontal shelf, which supports 

 the rhinencephalon, and at its anterior apex the hinder edge of the 

 median ethmoid is visible, which guides each olfactory into its covered 

 passage beyond. Considerable diploic tissue is found between the 

 tables of the vault of the cranium in this Albatross, and tbe skull as a 

 whole seems to be pretty well permeated by air. 



The sclerotals of an eyeball are comparatively small plates, with 

 irregularly serrated margins. They differ somewhat in their general 

 outline, and there seems to be no fixed plan as to the method in which 

 they shall overlap each other. 



The symphysial extremity of the mandible (Fig. 19) is formed very 

 much as it is in the Petrel, and evidently constructed upon the same 

 plan. Its symphysis proper is exceedingly short and the superior ex- 

 cavation deep. 



Old Albatrosses have a median process co-ossified upon the under 

 side of this with the bone. It is ensheathed in the horny integument of 

 the bill, receiving a separate piece to cover it in'that situation. The 

 process itself is sometimes long and sharp, directed backward in the 

 anterior ramal angle. It will be remembered that a somewhat similar 

 strueture was found in some of the Herons. 



The shape of the mandible as a whole in this Albatross is precisely 

 like the capital letter N/> as i 11 the Petrels. 



Each ramus is deeper behind than it is in front, the transition being 

 gradual, and lies principally in the vertical plane when the bird stands 

 with his beak to the front. 



The borders for nearly their entire length are rounded, the superior 

 symphysial one alone being sharpened, and the coronoid process is but 

 feebly pronounced. Both inner and outer aspect is for the most part 

 smooth ; the former for its anterior two-thirds is marked by a longi- 

 tudinal, thickened ridge, while the latter shows many branching rami- 

 fications sunken below the general surface, and foramina, arranged in 

 two rows, are carried to its anterior end. 



The surangular is usually pierced by one or two small foramina in the 

 same place as they appear in other water birds, where I have described 

 them, though commonly only one is seen. 



Albatrosses, in common with Auks, Gulls, Guillemots, and others, 

 have a fau-shaped process developed by the surangular, which remains 



