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. Hiucks 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 Anatida; are more or less subject to an occasional ru- 

 fous 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. 



^luch 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, to- 

 gether with a certain amount of individual and developmental dif- 

 ference. 



"When it has been shown that in another species of Cygnus (0. 

 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 rela- 

 tive position in the specimens of C. buccinator and in the so-named 

 C. jiassmori, referred to or described in this paper, only exhibits the 

 counterpart of such a change, it prepares us to believe, on the evi- 

 dence 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 ditferently aged birds, manifesting a gradual increase of the tracheo-sternal 

 protnl)erance. 



