448 C. J. Sundevall on the Wings of Birds. 



colours also_, the external aspect of the bill and feet (but 

 certainly not their structure), their smaller size and resi- 

 dence in trees, cause one to fancy that they are like the 

 Song-birds, with which they have constantly been confounded. 

 The case is different with Picus, for this genus appears to be 

 a true transitional form, which, from its wing-structure, 

 seems most to resemble the Song-birds ; but its want of the 

 song-muscles, the structure of its feet, and the arrangement 

 of the muscles of the wing, in combination with the above- 

 mentioned character of the small outer coverts, determine 

 most distinctly its place to be among the Cuckoo-like 

 birds. 



We have here endeavoured to show that although there are 

 manifold and considerable differences between the birds 

 which are destitute of the song-apparatus, nevertheless they 

 all possess a decided similarity of organization, owing to 

 which they can and must be grouped together as a single 

 great division of the class, in opposition to the Song-birds, 

 which have another very distinct fundamental structure, but 

 which present a very remarkable uniformity. This binary 

 division is therefore the first natural division of the class of 

 Birds ; the Song-birds must stand at one end of the series, and 

 next to them come the Pici, Coccyges, &c. The other end is 

 necessarily occupied by the Natatores. The Accipitres and 

 Gallinse must retain their place in the middle of the series, 

 which, however, certainly does not prevent our regarding 

 them as the most highly developed, if we choose to 

 do so. 



I have already developed these same views of the affini- 

 ties and scientific arrangement of the forms of birds in my 

 " Ornithologiska System,^^ published in 1835 in the Kongl. 

 Vet.-Ak. Handl. and they have only been strengthened by a 

 continued investigation, although many alterations in the more 

 special groupings have been rendered possible by an enlarged 

 knowledge. 



In order to give a summary of the more important of these 

 alterations the following Appendix is provided. 



