1S2 PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Three Swans, which vou Pelzeln iu 18G2 described as belonging to 

 immutaMlis, are in the present work introduced under C. iimcini, a spe- 

 cies which Hume founded iu 1871 on two immature specimens, and 

 which has usually been regarded as the young of C. gibhiis Bechst. 

 Thus we at preseut allow nine species of Swans. 



The C.passmori, described by Hincks in 1805, seems only to be a young 

 huccinator. Gijgnus davidi, which was described by Swinhoe in 1870, 

 does not belong to the Swans, but to the genus Coscoroha Eeichb. 

 amongst the Anathuc. (See p. 180.) 



Until Bechstein in 1803 indicated the genus Cygnus, the species be- 

 longing to this group were referred to the great Linn^AN genus Anas. 

 The new genus was soon commonly adopted, and remained undivided 

 until 1832, when Waglek* divided it into three, viz : Chcno^ns, Olor, 

 and Cygrms. 



At first I was inclined to regard all the Swans as belonging to only 

 one genus. But since Prof. Theo. Gill has drawn my attention to 

 several differences in the structure I have convinced myself that the 

 genera in question are as well founded as a greater part of genera among 

 the A^iatidw, which I never hesitated to admit. If one would adopt the 

 view of Mr. Seebohm,! that the color is the most important generic 

 criterion, only two genera ought to be established, the one white and 

 the other black ; but the greatest ditferences are even to be found be- 

 tween the white species, this fact, for one, showing the untenabiiity of 

 Mr. Seebohm's standpoint. The color can indicate where the limits of 

 a genus are to be drawn, and may in many cases be of great value as 

 instruction when the matter is doubtful, or may also add an important 

 character to the other ones, but it ought not to be the only or even the 

 main character of a genus, which should merely be based upon struct- 

 ural marks. 



In the matter now before us it will, however, be seen that if we admit 

 any subdivision of the genus, the black-necked Swan must be separated 

 from the Pala?arctic knob-billed Swan {Cygnus gihhus) and its congeners 

 to obtain equivalency with the different groups.J I therefore propose 

 the new genus ISthenelus, the number of recent genera thus being four. 

 For the fossil C.falconerl I have introduced a fifth genus, Palaeocycnus. 



SYNOPSIS OF THE GENERA. 



o'. Predominant color of the adults wbite; young with do^ny or feathered lores; ter- 

 tiaries and scapulars uoroial, not crisi^; tail longer than the middle toe 

 "with claw. 



• Eearlier than this BoiE had asserted the necessity of this divisou (Oken's Isis 1822, 

 p. 564, nat). 



tCat. Birds Brit. Mus., vol. v, p. viii : "These so-called structural characters have 

 no generic value at all." (!) 



tREiCHKNBACH, in his Naturg. Vog. Neuholl, p. 343, expresses the same opinion, 

 nowhere, however, as far as I cau detect, giving a name. 



