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Show 1867.] DR. J. MURIE ON CYGNUS BUCCINATOR. 13 This tracheal character reverses the similitude exhibited by the two sterna to Cygnus passmori and C. buccinator respectively. Moreover it would seem that no two sterna of all mentioned are identical in every point. Finally.-The foregoing details regarding external and internal points of variation, if taken together and placed in juxtaposition with those of the authors mentioned, lead partly to the decision thrown out by Prof. Hincks himself, that there is a variability " or succession of degrees of development according to age;" in the Trumpeter Swan (Cygnus buccinator) it may be also in sex, although I am rather of opinion that it is an individual difference not always dependent on age or sex. Whichever of these may have most weight, the distinctions which he at first attributed as specific appear in reality not to be valid. In favour of this view, we have three specimens all agreeing in common, and yet differing slightly from his and Yarrell's accounts of the colouring. For the rufous coloration does not necessarily imply specific value, as it is well known to ornithologists in general that many of the Anatidce are more or less subject to an occasional rufous tinge, the reason of which is not satisfactorily ascertained. The Teal and Pintail are often conspicuous in this respect, and the head is generally so affected. Much dependence cannot be placed on the weight or even on the measurements of the body, as age and condition seriously affect them. In birds the sternum is the bone in which most dependence can be placed as indicating affinities, or even specific difference *; and this, along with the disposition of the trachea, is markedly so in the genus Cygnus, as Yarrell has well demonstrated. But here in C. buccinator we have in the variation no essential typical alteration, but simply a gradual growth and change in size of the parts, together with a certain amount of individual and developmental difference. When it has been shown that in another species of Cygnus (C. bewickii) the osseous expansion destined to protect the enclosed loop of the trachea alters considerably, but within certain limits, from the young to the adult stage f, and that this alteration in size and relative position in the specimens of C. buccinator and in the so-named G. passmori, referred to or described in this paper, only exhibits the counterpart of such a change, it prepares us to believe, on the evidence adduced in our data, that Yarrell's and Hincks's bird are one and the same, and that Cygnus buccinator is alone the proper specific name to be retained by naturalists. * Prof. Owen truly says the sternum is "the main characteristic of the bird" (On the Anatomy of the Apteryx, Trans. Zool. Soc. vol. ii. p. 290). t See Trans. Linn. Soc. vol. xvi. (1833) p. 447, tab. 25, where Yarrell figures three differently aged birds, manifesting a gradual increase of the tracheo-sternal protuberance. |