446 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Apr. 1 1, 



Fi^. 28. 



T- ^^ rrf I lf\ J 



■y-^b 



Buceros. 



a. The apertures whicli lead into the cavity of tlie rostrum. Ji. The posterior 

 part of the helmet. The other letters as before. [N.B. By mistake a ^ in- 

 .stead of a + is put opposite the rudimentary left basipterygoid process.] 



a median septum ; and these lead into the cavity which, for the most 

 part, occupies the interior of the rostrum. I cannot say whether 

 this septum is a prolongation of the vomer, or whether it belongs to 

 the large and spongy maxillo-palatines, which bound the apertures in 

 question and meet in the middle line with one another and with the 

 vomer. In this genus the external nasal aperture is placed, as is 

 well known, immediately in front of the anterior and upper part of 

 the orbit. It leads into a horizontal passage, with thin, but dense, 

 bony walls, which passes at first almost directly inwards, and then 

 turns forwards at a right angle. The inner wall of the forwardly 

 directed portion of the passage presents a rounded ridge, by which 

 its cavity is imperfectly divided into an upper and a lower passage. 

 The lower opens into the cavity of the rostrum ; the upper bends 

 back and opens into a vaulted chamber, to the roof of which a small 

 pyriform "turbinal" is attached by its narrow end. From the inner 

 end of this chamber a passage leads directly downwards and applies 

 itself closely to that of the opposite side. At the level of the lov/cr 

 margins of the external nasal apertures the partition between the two 



