MR. W. K. PARKER ON THE OSTEOLOGY OF BALiENICEPS REX. 289 



'principal frontals.' In the Heron these processes are bridged over by bone, thus 

 walling-in the olfactory nerve. The anterior keeled margin of the pre-sphenoid of Balse- 

 niceps is sinuous, but vertical above, whilst its lower half retires a little before coalescing 

 with the projecting ' rostrum.' In the Heron this centrum retires very much more, and 

 the inferior antorbital process, after bridging over the olfactory nerve, sends an elegant 

 curled lamina downwards, outwards, and forwards. This process, so large in the 

 Albatros and many other birds (e. g. Snipes, Woodcocks, Pigeons, Goatsuckers, Owls, 

 Parrots, &c.), but almost obsolete in the Balseniceps, Boat-bill, and Adjutant, in Gal- 

 lincE, Anatinae, and in those wading, swimming, and diving birds in which the orbital 

 margin is very incomplete, is a ' pterapophysis',' and its special homologue maybe well 

 seen in such mammals as the Rabbit. Serially, it is homologous with those ' pterygoid 

 plates ' spoken of as pertaining to the post-sphenoidal and occipital centrums. 



The pre-sphenoid of Balseniceps is thick and cellular above, in front, and below ; its 

 middle part behind helps the orbito-sphenoid to finish the flat inter-orbital septum. In 

 our description of the orbito-sphenoids, we spoke of the deficient ossification of this 

 septum ; we will add, that its extreme development, as to thickness and cellularity, is 

 in Owls, especially the Screech Owl {Strix flammea) , and in Goatsuckers {Caprimulgus). 

 In the diurnal Raptores it is more or less imperfect, as also in the Pigeons and Galli- 

 naceae; in Parrots, Toucans, Woodpeckers, and most of the Scansores, it is very 

 perfect, but not in the Hornbills. It is very imperfect in the Corvine, Passerine, and 

 Sylviine groups, so nearly related to each other, and so potent in genera and species. In 

 the smaller Ardeine birds (e. g. Ardea, Botaurus, and Cancroma) , in Cranes, Spoonbills, 

 Curlews, Plovers, Godwits, Rails, Coots, Jacanas, Grebes, Divers, Auks, Gulls (the 

 smaller species), Gannets, Cormorants, Penguins, Petrels, and even in the Albatroses, 

 the inter-orbital septum is more or less incomplete. In the larger relations of Bateniceps 

 this septum is perfect {e.g. Ciconia alba, and in Leptoptilus), and the same may be said 

 of the Struthionidce. For an account of the manner in which the olfactory chambers 

 encroach upon the sides of the pre-sphenoid in such birds as the Ostrich, Dinornis, 

 Apteryx, Cassowary, and Dodo, &c., see Professor Goodsir's paper (op. cit. p. 156). 

 We may remark, however, that the Common Duck and the Albatros are familiar but 

 very beautiful instances of birds in which these pre-sphenoidal nasal cavities are large 

 and well- developed. 



Lacrymal. (PI. LXV. figs. 1 & 6, I.) 



The next bone to be spoken of (the lacrymal) belongs properly to the face, but its 

 important relations with the sphenoido-frontals and antorbital processes (pterapophyses) 

 of the pre-sphenoid make it convenient for it to be dealt with at once. 



' Where there is a distinct centre for this process, it is something more than a ' pterapophysis,' as may be 

 seen in young Pigeons ; in these birds it evidently is, what Professor Owen calls it, the homologue of the human 

 •os planum.' 



