12 DR. J. MURIE ON CYGNUS BUCCINATOR. [Jan. 10, 



rings I shall mention hereafter, but here only point out they are 

 like Yarrell's plate, and not Hincks's figure of them in his C. buc- 

 cinator. 



The second figure (fig. 2) represents the sternum of the skeleton 

 in the British Museum, contrasted with that of its companion bird 

 (fig. 1), The disposition and inflexions of the trachea correspond 

 to the one first described, and with it confirm the accuracy of Yar- 

 rell's distinctions between the Hooper, with one vertical sterno- 

 tracheal convolution, Bewick's Swan, with a single horizontal one, 

 and the Trumpeter with two, one in each of these directions. 



In the specimen in question (fig. 2) the posterior tracheal osseous 

 eminence is situated nearly equidistant between the right and left 

 sides. Its length is not so sharply defined as in the other ; but its 

 measurements correspond to about 3 inches long and 1| broad. 

 Neither is it so lop-sided in form, and it Avants the posterior trun- 

 cation present in its fellow bird, while its surface rises from each 

 margin equally, until attaining in the middle a height of g an inch 

 above the level of the horizontal sternal plate. There is a very slight 

 foramen or deficiency of bone towards the left side. 



The anterior tracheal bony prominence is ovoid, and not heart- 

 shaped as in the College specimen. The depression or shelf upon 

 which the end of the trachea and bronchise rest is not so broad nor 

 by any means so scooped out as in the other. The greatest height 

 which the bone reaches in this cavity is but H inch, and the sides 

 are less perpendicular. 



The sterno-tracheal elevations in the points mentioned above, par- 

 ticularly the height of the anterior and less magnitude of the poste- 

 rior, agree closely with those of C. ijassmori. 



The posterior sternal emarginations in the British Museum spe- 

 cimen are both uncovered, and neither of them is so deep or smooth- 

 edged as in the companion bird. The greatest length of the sternum 

 is 8j, and its breadth behind 3:f inches. 



The costal edges run almost parallel ; the terminal manubrial and 

 ensiform plates are comparatively the narrowest ; and the sternum 

 altogether is shallower inside, or at least shelves more gradually 

 towards the middle. 



Over and above these strictly sternal differences, the rings of the 

 trachea in the two birds present variation. In the British Museum 

 specimen the bony rings, from the bend of tlie neck to where the 

 trachea enters the keel, are intermittingly broad and narrowed or 

 wedge-shaped on the upper a/\d lower halves; in other words, each 

 half of the ring is unequal in breadth and dovetailed to those on 

 either side of it, just as Ilincks has depicted {loc. cit. p. G. f. 8) in 

 the trachea of his C. buccinator, where it divaricates at the bronchia?. 

 In the College specimen the rings are nearly uniform in breadth, or 

 very sparingly show this peculiar kind of wedge-shape. In both ■ 

 specimens the trachea, after its emergence from the sternum, has 

 wider, regular rings, such as Yarrell's sectional view illustrates; but 

 the College specimen has here and there a tendency to revert to the 

 unequal form. 



