1867.] PROF, HUXLEY ON THE CLASSIFICATION OF BIRDS. 449 



I am disposed to regard this ossicle and its fellow as the representa- 

 tives of the vomers, which, if this interpretation he correct, remain 

 exceptionally distinct from one another, but unite with the palatines. 

 The antero-internal angle of the body of the palatine bone sends 

 forwards a slender process, which forms the inner boundary of the 

 posterior half of the palatine foramen. 



The maxillo-palatines are broad plates, which appear to terminate 

 by rounded internal edges close to and above the external margins 

 of the palatines. But a tough membrane extends inwards from the 

 free edge of each maxillo- palatine and meets with a delicate longitu- 

 dinal ossification of the septum {a, fig. 30). Opposite the anterior 

 termination of the external nasal aperture this ossification is con- 

 nected with a transverse bar of bone, which stretches from one prse- 

 maxilla to the other, and shuts off the cavity enclosed by the prse- 

 niaxillse from the nasal chambers. The latter are greatly complicated 

 by the development of twisted "turbinal" plates in connexion with 

 the nasal and piemaxillary bones and the ethmoid. 



A prolonged and careful study of fresh specimens will be necessary 

 before the arrangement of the parts in Picus can be thoroughly un- 

 derstood. In the meanwhile it is clear that, in this genus, the palate 

 differs very widely from that observed in any of the preceding 

 " cuculiform " genera. 



In Picus majoi- the palatine bones have the same structure and 

 arrangement as in P. viridis, except that their posterior ends are 

 transversely truncated and the postero-external angles are even a 

 little produced. The maxillo-palatines are much smaller than in the 

 preceding species, and their inner rounded edges do not nearly reach 

 the level of the outer edges of the palatines. 



Picus canus resembles the preceding ; but the postero-external 

 angles of the palatines are rather better marked, and the maxillo- 

 palatines a little larger. 



Picus mecUus presents no difiFerence of importance, except that 

 the inner laminse of the palatines, obsolete in the other genera, are 

 a little better marked, especially behind. 



In Picus minor distinct maxillo-palatines can hardly be said to be 

 present, the maxillary presenting only a slight dilatation at the point 

 where they should exist. Minute points of bone projecting from 

 the inner edges of the palatines alone indicate the position of the 

 process (c) in Picus viridis and of the prolongation of the antero- 

 iiiternal angle of the body of the palatine. The "oval foramen" 

 consequently is indicated only by a slight excavation of the inner 

 margin of the palatine. 



This species of Picus prepares one in some degree for the struc- 

 ture observed in Yunx (fig. 31). Here the ascending processes of 

 the palatine bones are produced forwards into long and slender pro- 

 cesses, slightly swollen at their anterior free ends, which may represent 

 anchylosed vomers. The inner edges of the short and broad bodies 

 of the palatine bones a])proach so nearly as only to leave a cleft for 

 the posterior nares. The antero-internal angles are acute, but not 

 greatly prolonged. The anterior processes of the palatines are very 



Proc. Zool. Soc— 18()7, No. XXIX. 



