174 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



OUTliIIVES OF A MOIVOGRAPH OF THE CY«I\IIV^.* 

 By L.EONMARD STEJIVEGER. 



["It is better to err on the side of minuteneas tb<an of vagueness."— GossE. ] 



CYGNIN.E BONAP. 



1838. — Cygninw Bp. Comp. List. p. 55. 



1850. — Cygnidw Kaup (fide Gray). 



1852, — Olorinw Reichb. Syst. Av. p. x. 



18G0. — Cijcnidw Des Mues, Tr. Ool. Ornith. p. 537. 



DiAGN. — Anatidce having the kind toe without iveb and the lores naJced, 

 coincident with reticulate tarsi, the latter shorter than the middle toe tcith 

 claw. 



The i^receding marks combined appear to express the essential char- 

 acters of the Cygnincc. By this dia.5>-nosis I follow Mr. SundevallI 

 in excluding the genus Coscoroha Reichb., which has the lores feathered 

 at all ages. As early even as Euppell's monograph of tlie genus 

 Cygnus, (Mus. Senkenb. Ill), it was separated from the Swans. Here, 

 however, it may be remarked, that this diagnosis refers only to the 

 adult birds, because the young have the lores more or less downy or 

 feathered, except in the genus Chenopis, which has the loral space 

 naked at all ages. The removal of Coscoroha to the Anatimc will be 

 discussed more explicitly below. The criterion " tarsi reticulate " further 

 excludes the genera Cairina Flem. and Plcctropterns Leach, which, it 

 is true, have the lores naked, but the tarsi of which are scutellate in- 

 stead of reticulate. Anseranas Less, has certainly both naked lores and 

 reticulate tarsi, but differs in having the tarsus longer than the middle 

 toe with claw. 



Anatidce which do not at once unite all the above characters conse- 

 quently belong to one of the other subfamilies. 



The whole ftimily Anatidw forms, as to structural features, a very 

 homogeneous group, and intermediate links are everywhere to be found. 

 Thus it is very difficult to define the subfamilies anatomically, and to 



"The present treatise comprises merely the ontlines of a monograph of the Swans, 

 intended by the author to bo mnch more complete, but which liis departure for the 

 Commander Islands prevented him from fini^shing according to the original plan. The 

 paper contains so many valuable hints and so much important information upon this 

 interesting group of birds, that it has been thought advisable to publish in it its pres- 

 ent form, as preliminary to the more elaborate monograph contemplated by the au- 

 thor after his return. — R. R. 



tTent. Meth. Av. Disp. p. 147. 



