649 



CYGNUS. SWAN. 



This genus is formed of a small number of species, 

 remarkable for tbeir great size, they being the largest birds 

 of the order to which they belong, and distinguishable from 

 the Geese and other allied genera by the extreme bulk of 

 their ovato-oblong, full, and somewhat depressed body ; their 

 excessively elongated and slender neck ; and short, consider- 

 ably compressed tarsi. The head is of moderate size, oblong, 

 compressed, and rather flattened in front. 



The bill rather longer than the head, large, higher than 

 broad at the base, gradually becoming more depressed, of 

 nearly equal breadth throughout, and rounded at the end ; 

 upper mandible with the lateral and superior basal margins 

 at first semicircular, forming two short angles, but ulti- 

 mately obliterated by the disappearance of the feathers, which 

 leave a large space extending to the eye bare ; the ridge 

 broad and flattened at the base, gradually narrowed, convex 

 toward the end, the dorsal line sloping, a little concave at 

 first, the sides nearly erect at the base, gradually more de- 

 cimate and convex toward the end ; the unguis generally 

 roundish, large, and convex ; the edges soft, marginate, and 

 scrobiculate, straight, and concealing the narrow, blunt tips 

 of the slender, little elevated lamellae ; lower mandible with 

 the intercrural space very long, of moderate width, its mem- 

 brane bare for two-thirds, the short dorsal line convex, the 

 crura long, narrow, their lower outline slightly re-arcuate, 

 their sides sloping outwards and convex, the edges elevated, 

 inclinate, denticulate Avith the short outer extremities of the 

 lamellae, the unguis roundish and little convex ; the gape- 

 line nearly straight, commencing anteriorly to the margin of 

 the feathers on the forehead. 



