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Show 8 DR. J. MURIE ON CYGNUS BUCCINATOR. [Jan. 10, leche) might be said to be the South-African prototype of the West- African jEquitoon (Adenota kob), notwithstanding that these forms are found within a short distance of a parallel northern latitude. In the one case the animals inhabiting the southern equinox are darker and larger than those of the northern equinox. Examples might be given of other animals presenting analogous shades of difference : for instance, the Giraffes found north and south of the equatorial line have by some naturalists even been considered specifically distinct; and other authors point out like shades of difference in the Elephant &c. How far such suggestions are surmise, and how much based on wider generalizations, more extended facts would better determine; but such thoughts do arise on considering what has been shown to occur in the fauna of other extensive continents, e. g. in the insects and birds of South America. 2. O n Cygnus buccinator, Richardson, and Cygnus passmori, Hincks. By J A M E S M U R I E , M.D., F.G.S., Prosector to the Society. The Rev. W. Hincks, F.L.S., Professor of Natural History in the University of Toronto, Canada, communicated to the Linnean Society, on the 21st January 1864*, a short but suggestive paper, wherein he gave to a specimen of Trumpeter Swan the name of Cygnus passmori. In a letter dated 10th of April, and subsequently read on the 5th of M a y of the same year, he, however, threw out hints of the possibility of an error of judgment on his part, as further investigation led him to believe that the difference in individual specimens which he at first was inclined to regard as specific might really not be such, but rather be attributable to gradation of form connected with age. The facts brought forward by that gentleman, so far as I know, have thus been left in uncertainty ; and hence arises the interrogation, Are there characters sufficiently distinct and constant to warrant a separation of the Trumpeter Swan into two species ? or is the variation in individual form merely a modification or progression of growth as suggested by Prof. Hincks ? I will in the present paper endeavour to answer these questions, at least as far as the evidence goes which the examination of three specimens affords. These were added to the Zoological Society's Collection in the Regent's Park on the 10th of M a y 1866, and assumed to be the true Trumpeter Swan (Cygnus buccinator of Richardson). Two of the birds died a short time after their arrival, and afforded m e an opportunity of examining that part of the skeleton in which the chief grounds of specific separation are found, viz. the sternum which in * Published in the ' Journal of the Proceedings of the Linnean Society (1865), pp. 1-7. ' ' |