98 . NATURAL HISTORY OF KERGUELEN ISLAND. 



are: two deep fossae just above and parallel to the sux)erior orbital mar- 

 gins, a prominent bony crest (for the support of the caruncle) in front 

 of these, the large size and subcircular form of the foramen magnum — 

 all of which will be described in detail below. 



Occijntal bone is convex inferiorly and irregularly trapezoidal in 

 shape. Its crest is less prominent than usual, although quite distinct; 

 shaped like a bow, with its extremities distinctly defined as far as the 

 superior border of the meatus auditorius externus. The condyle is small 

 and spherical (not nicked, as in Gallince). Foramen magnum is nearly 

 circular in outline, its anterior border being cut oft' so as to form a high, 

 broad arch. It measures in antero-posterior diameter 0.21, in trans- 

 verse diameter 0.32 inch. On each side of the condyle is a broad space 

 for ligamentous attachments ; laterally and posteriorly to these its 

 paroccipital (?) portions extend downward as vaginal processes, protect- 

 ing the posterior border of the external auditory meatus. From the 

 foramen magnum to the crest extends upward a prominent median 

 ridge, flanked by lesser ridges on each side from the lateral portions of 

 the foramen. 



Sphenoid is irregularly pyramidal in shape, being produced forward into 

 a long cultrate spine (baslsplienoid), embraced by the two prongs of the 

 vomer and upon which ride the palatine and pterygoid bones. There are 

 BO distinct basipterygoid processes. Only the marginal portions of the 

 basisphenoid contribute to the floor of the orbits, its orbital plates pass- 

 ing upward and outward to complete a septum between the brain and 

 orbit. This septum is perforated in the median line by two irregular 

 foramina for the transmission of the optic and olfactory nerves. The 

 inferior (optic) foramen is heart-shaped, the apex of the figure being 

 directed upward, and the lateral lobes much prolonged. The superior 

 (olfactory) foramen presents the outline of the ace of clubs. As these 

 are the chief anterior foramina of the brain-case, they probably transmit 

 other nerves distributed to the orbit and face, as well as the olfactory 

 and optic. Rising from the superior margin of the basi-sphenoid is the 

 inter-orhital septum, perforated anteriorly in this species by an irregular 

 vacuity, and posteriorly by an extension forward of the optic and olfac- 

 tory foramina already noted. The interorbital septum is, however, 



ridge very prominent j * » * * ridges for the attachment of the masseter mnscles 

 strongly marked." {Osteologia Avium, London, 1867,2?. 176.) As we cannot believe there 

 is any marked difference in the skulls of C alba and C. minor, we simply fail to ap- 

 preciate the pertinence of the author's remarks in this case. 



