ORGAN OF SMELL IN BIRDS. 



131 



52 



Bill aud nostrils of the Petrel. 



directed forward. In the Petrels the nostrils are produced in a 

 tubular form, parallel to one another for a short distance alono- 

 the upper part of the mandible, with the ori- 

 fices turned forwards, fig. 52, a. 



The septum narium, fig. 53, e, e, is, in 

 general, complete, and is partly osseous, partly 

 cartilaginous. It is perforated in the Swan 

 just opposite the external nostrils, and in the 

 Toucan, lower down, ib. b. The surface of 

 the septum is rugose in this bird, and the pituitary membrane 

 which covers it is highly vascular. The parietes of each of the 

 nasal passages give attachment to three turbinal laminae. The 

 inferior one is a simple fold adhering to the lower and anterior 

 part of the septum narium ; it is partially ossified in some Ba- 

 sores. The middle turbinal is the largest : it is of an infundibular 

 figure, and adheres by its base to the septum and externally to the 

 side-wall of the nose. It is convoluted with two turns and a half 

 in the Anserine Birds, but in many birds it is compressed and 

 forms only one turn and a half. The superior turbinal t, h" , 



53 



Section of head, showing vertical nostrils, Toucan (Ramphastos). xx: 



fig. 56, generally presents the form of a bell ; it is more or less 

 ossified at its base, but mostly cartilaginous, and adheres to the 

 upper part of the prefrontal. It is hollow, and divided into 

 two compartments, which are prolonged in a tubular form ; the 

 internal one extends toward the orbit, the external terminates 

 behind the middle turbinal in a cul-de-sac. The turbinal 

 supports of the pituitary membrane may be membranous 



K 2 



