210 Mr. A. 11. Wallace on the Natural Arrangement of Birds. 



mating to that of the Cuckoos. In their habits too they are 

 equally distinct : they hop and cling, but never climb, and they 

 live almost exclusively on soft fruits. We must therefore con- 

 sider them as a distinct family, and place them in the vicinity of 

 the Toucans and Cuckoos. 



We will now proceed to the consideration of those groups, 

 about the propriety of including which in the Scansorial tribe 

 considerable difference of opinion has existed. These are the 

 Turacos {Musophagidce), the isolated genus Opisthocomus, and 

 the Certhiada including the Dendrocolaptid(e. These last have, 

 we believe, only been so placed by Messrs. Vigors and Swainson, 

 but as their classification claims to be pre-eminently "The INatural 

 System,'^ and as it has still some advocates, it deserves to be 

 carefully examined. What are the characters then by which the 

 Dendrocolaptid(S are supposed to be united to the Picida ? They 

 appear to be these : both are true Climbers, both have a rigid 

 tail which assists them in maintaining an erect position, and 

 both feed on insects which they obtain upon the trunks and 

 branches of trees. On the other hand, they present many and 

 important differences. The long, slender, curved bill and short, 

 horny, non-extensile tongue of the Creepers are very far removed 

 from the strong straight bill and extensile barbed tongue of the 

 Woodpeckers. But this, it may be said, is of no importance, as a 

 similar difference exists in the other families admitted into the 

 Scansores. This is true ; but then those birds agree in having 

 the same form of feet, which is of far more importance in this 

 case than it may at first sight appear, for we shall be able to 

 show not only that the Creeper's foot is very different from the 

 Climber's, but that it is further removed from it than is that of 

 any other of the Passeres. iiiJ 



The characteristic form of foot in the Certhiada and Dendtd^ 

 colaptida is to have the toes placed normally, three forward and 

 one backward, and to have the forward toes all connected to- 

 gether at their bases, particularly the outer toe, which is gene- 

 rally longer than the inner, and often connected to the middle 

 toe as far as the second joint. The result of this conformation 

 is, that the forward toes do not spread much laterally, but form 

 one line of support opposed to the hind toe. This hind toe also 

 is remarkably long and powerful, and armed with an equally 

 powerful claw. This peculiar structure has been gradually ar- 

 rived at, through the most nearly allied families of Passeres. 

 Passing from the Wagtails and Larks through the AnahatidcB to 

 the Certhiadce, Sittidce, and Beiidrocolaptidce, we find the outer 

 toe gradually more and more united to the middle one, and the 

 hind toe becoming gradually larger and more developed; so 

 that we are justified in asserting that we see here that peculiar 



