602 Zoological Proceedings of Societies. 



mation in form to the breast-bones of the Mergansers next in 

 succession. The increase in the length of the ribs and the gradual 

 approach by the Ducks and Mergansers to the form of the more 

 perfect salt-water Divers, included in the genera Colymbus, Uria^ 

 and Alca^ was pointed out by a comparison with a skeleton of 

 one species of each genus, the elongation of the sternum and ribs 

 forming at length a complete defence to the abdomen and flanks, 

 by which the birds are enabled to resist pressure when diving. 

 Several other collateral relations of minor importance were also 

 noticed. In conclusion it was remarked that the external cha- 

 racters were also sufficiently marked to furnish a ready distinction 

 between the divisions, the Ducks referrible to the first being cha- 

 racterized by length of neck, wings, and tarsi, and by their hind 

 toe being free or without pendent lobe ; while in those of the 

 second the neck, wings, and tarsi are shorter, the latter com- 

 pressed, and the hind toe lobated. 



February 13. — The reading of the paper entitled Remarks on 

 the Comparative Anatomy of certain Birds of Cuba^ with a view 

 to their respective places in the System of Nature^ or to their 

 Relations zoith other animals; by W. S. Mac Leay, Esq., was 

 continued. 



February 27. — Mr. Yarrell exhibited specimens of several fe- 

 male Pheasants in which the plumage had undergone a cbange so 

 considerable as to present a striking resemblance to that of the 

 male. In explanation of the causes of this change, and of analo- 

 gous alterations in the plumage of other birds, he entered into a 

 series of remarks, which were subsequently embodied into a paper 

 read before the Royal Society, and printed in the Philosophical 

 Transactions. An abstract of this paper has already been given at 

 p. 291 of our present volume. 



March 13. — Mr. Bell exhibited numerous specimens and draw- 

 ings of the Testudinata, Klein, for the purpose of illustrating the 

 natural affinities and distribution of this order of Reptilia. He 

 pointed out five principal forms which he regarded as types of so 

 many families, the Testiidinidce, Emydidce, Trionychidce^ Sphar- 

 gidce, and Cheloniadw, and dwelt at some length on the characters 

 by which each is distinguished from the others, and also on those 



