414 ON THE PETEELS COLLECTED DURING 



capsules near their anterior extremity, continuous anteriorly with the 

 premaxillae, united together in the median line, and externally abutting 

 on the outer and lower wall of the nostril. 



Zool. Ohall. The skull above the orbits is always deeply excavated for the fossae in 

 pt^xJp. 43! which lie the nasal (" supra-orbital ") glands. In the Albatrosses there 

 is a strong raised external border to the fossa posteriorly, prolonged 

 from the post-orbital processes, whilst externally this floor, here per- 

 forated by numerous apertures, is deeply excavated. 



The post-orbital processes are large and strong. The temporal fossae 

 are well-developed, nearly meeting across the middle line in most, 

 though in the Albatrosses separated by a considerable interval. The 

 occipital plane is inclined downwards and forwards, but in the Alba- 

 trosses is nearly vertical. In these birds the digastric fossae are 

 continuous, meeting each other in the middle line, whilst in the other 

 Tubinares they are separated to a greater or less extent by the wide, 

 smooth, convex cerebellar eminence. 



As might be expected, all these fossae and their bounding ridges are 

 much better developed in the large Albatrosses and Petrels (Ossifraga, 

 Majaqueus, &c.) than in the small Procellariidse and Oceanitidse, in which 

 the skull is comparatively smooth, of much thinner texture, and with the 

 cerebellar eminence occupying a much greater extent comparatively. 

 The interorbital septum is well ossified in the larger species, most so in 

 Diomtdea exulans, whilst in the smaller ones it is very extensively 

 fenestrated. 



The lachrymal bone is always well developed, but varies in form in the 

 . different groups. In the Oceanitidae and the small Petrels of the Pro- 

 cellaria- group it is T-shaped in form, the long arm of the T being hori- 

 zontal, extending forwards from the body of the bone (which is nearly 

 vertical) to articulate with the external descending process of the nasal 

 bone, just behind the level of the end of the nostril. Between it and the 

 rest of the skull lies a considerable oval fenestra, occupied by membrane 

 in the recent state. The ascending process articulates with the frontal, 

 forming a well-marked, backwardly-directed, antorbital process, whilst 

 the descending process descends downwards towards the jugal arch, to 

 which it may be united by ligament articulating internally with the con- 

 siderable antorbital plate of the ethmoid (" ectethmoid," Parker). 



In Pelecandides, Puffinus, Adamastor, and Majaqueus it has the same 

 relations, but is more triangular in form, and closely abuts on the 

 cranium superiorly, the fenestra being reduced thus to a chink. In the 

 Albatrosses it also remains separate from the skull, and the anterior 

 limb is but little developed as compared with the vertical part, which is 

 swollen, excavated by air-cells, and forms above a strong antorbital 

 process. It loses its connection with the ethmoid. In the remaining 

 genera the lachrymal does not exist as a free bone, being firmly anchy- 



