ALCAD^. 



Tl HE Alcadae are discriminated from the rest of 

 the Natatores by the very backward position of their 

 legs, which in some of the genera are placed at the 

 extremity of the abdomen. The beak is of various 

 forms, but it is generally much compressed, and often- 

 times transversely grooved on its sides ; towards the 

 tip it is bent downwards, and the upper mandible is 

 sometimes furnished with a notch : the nostrils are 

 either linear and parallel to the edge of the beak, or 

 rounded and placed in a deep furrow ; in some they 

 are hidden in a bed of silken feathers, and in others 

 they are exposed. The wings are very short, and in 

 some genera the quill-feathers are entirely wanting. 

 The legs are furnished either with three or four toes. 



From the above characters it is evident that the 

 genera comprised in this family differ considerably 

 from each other ; in fact, there is so marked a dif- 

 ference that they may readily be divided into two 

 sections or sub-slirpes, 



DIVISION I. 



Rostrum plerumque valde compressum, scepe transversim sul- 

 catum ; pedes tridactyli ; alae breves. 



generally much compressed, and often transversely grooved ; 

 feet three-toed ; ivings short. 



The birds which are included in this division are 

 all natives of the northern regions : thpy fly well, 



