| OCR Text |
Show 446 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Ap Buceros. a. The apertures which lead into the cavity of the rostrum, b. The posterior part of the helmet. The other letters as before. [N.B. B y mistake a * instead 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 lower margins of the external nasal apertures the partition between the two |
