36 1 STRUCTURE AND CLASSIFICATION OF BIRDS 



Synthliborhatnphus antiqmis has also a perfectly typical 

 tracheo-bronchial syrinx, the first bronchial semi-ring (to 

 which intrinsic muscles are fixed) being longer and deeper 

 than those which follow. Phaleris is similar. 



Uria columba distinctly differs from Lomvia troile (with 

 which it is often considered to be congeneric), and is an 

 approach towards a type of syrinx to be described imme- 

 diately, but with certain peculiarities of its own. 



A dozen tracheal rings in front of the last are very 

 thin (more particularly in front), and have, therefore, wide 

 membranous intervals. The last tracheal ring, however, is 

 stout and ossified ; it appears to be composed of two closely 

 adjoined ; posteriorly three rings enter into the formation 

 of the tracheal box. The first bronchial semi-ring is very 

 much arched, so much so that laterally it conceals the last 

 tracheal rings. To it the intrinsic muscles are attached. 



In Ceratorhina monocerata this state of affairs is ex- 

 aggerated. Not only the first, to which muscles are attached, 

 but the second bronchial semi-ring is very convex upwards, 

 forming, indeed, the half of a rather elongated ellipse, as 

 shown in the figure (fig. 177). The last two tracheal rings 

 are ossified and closely connected. The last twelve tracheal 

 rings are shallow vertically and leave considerable mem- 

 branous interspaces. 



In Lunda cirrhata there is an almost identical syrinx, 

 but the last tracheal rings are not particularly thin in front. 



Fratercula arctica and F. corniculata are sufficiently 

 similar to need no special description. 



The tongue is generally fleshy, elongated, triangular, and 

 spiny only at the base. 



The relative proportions of the Uver lobes not only vary, 

 but the absolute size of the organ varies greatly. 



A gall bladder is always present. There is no crop. 



The cccca are usually mere nipples, -35--25 inch in length, 

 but in Alca tordd one inch. The length of the small 

 intestine in Fratercula arctica is 28'5 inches, in Alca tunla 

 49 '5 inches. 



From the characters displayed in the accompanying 



