Page:The Emu volume 8.djvu/19

 (Dffidal dDrgan oi the .^ustvakeiait ODrnithoIogist©' Euion. " Bir^s of a fcatbcr."

Vol. VIII.] 1ST JULY, 1908. [Part 1.

A Synopsis of the Genera and Species of Cygnin.

The few species of Swans known to science form a comparatively well-defined group, usually, and proba])ly rightly, considered of sub- family rank in the great family Anatidce. The genus Coscoroba, Reichenbach, by some authors associated with the Cygninæ, is undoubtedly a Duck, and belongs among the Anatinæ, although it forms to some extent a transition to the Swans.

With regard to the genera to be recognized in the sub-family Cygnince there has been considerable difference of opinion, but most authors admit only two^not counting, of course, the recently described Archæcycnus, De Vis.* Including this, there seem to be, however, five groups that are clearly of generic rank, and that rest upon characters quite as good as those adduced to separate the two current genera. The genus Palceocycmis (Stejneger), founded on the gigantic Cygnus falconeri of Parker, from Malta, seems to be undoubtedly valid, as this bird conspicuously differs from true Cygnus in its relatively short thigh bone, long tarsometatarsus, and in the very thick, abbreviated phalanges of the toes, showing thus no little vergence toward the Anserince. The separation of Cygnus melancoryphus as a generic type,t however, is not maintainable, since this species is strictly congeneric with those of Cygnus proper. Although the diagnostic points given by Dr. Stejneger for the separation of Cygnus from Olor% are all insufficient, there exist, neveitheless, excellent characters, both external and anatomical — particularly the latter — which, it is hoped, may now finally establish these much-abused groups. The genus Olor differs from Cygnus in lacking any knob, or tubercle, at the base of the culmen, in having a more or less evident bronchial dilatation, and in having the trachea looped and entering the sternum.

A key to the living genera of the sub-family sets forth their salient characters in more grcnphic form : — a.— Tail longer than middle toe with claw ; tertials and scapulars smooth. t Stejneger, Proc. U.S. Nat. Mus., v., 1882, pp. 183, 185. JProc. U.S. Nat. Mus., v., 1S82, p. 183.
 * Ann. Queensl. Mus., No. 6, 1905, p. il.