138 
ON THE CLASSIFICATION OP BIRDS. 
marks out and effects the change we have just intimated, 
and all this is accomplished within the limits of a single 
genus.* We have already had occasion to illustrate 
this very beautiful transission, as shown by the gradual 
change exhibited by the structure of the tail (101.), and 
it is equally so if we merely looked to the foot : that of 
Synaliajcis dnnamomem is of the same robust form as its 
congeners, but the toes, both before and behind, are 
longer, and their claws more slender, especially the 
hinder one. The tail preserves the broadness peculiar 
to Synallaxis, but then it assumes the pointed and 
almost naked ends of Ccvthia fumitiaTis : a more beau- 
tiful union of the characters of two genera cannot, per. 
haps, lie exhibited in the whole circle of ornithology ; 
and so much may be taught by frequent examination of 
these two species, in conjunction with a typical example 
of Syn(dl«ixis'\ , that they are the first birds which every 
ornithologist should possess, who wishes to study, not the 
bare and technical nomenclature, hut the true philosophy 
of our charming science. We thus arrive at a group 
(forming our sub-family of Certhianw) which answers 
to the description already given, that is, where nature 
gives a higher development than she has hitherto done, 
to every organ employed in climbing, so as to constitute 
tlie Certhiana the pre-eminent type of the scansorial 
creepers. We regret our space will not permit us to 
trace this development in any other member than the 
foot. Commencing, then, with that of the common 
creeper, we obseive all the indications exhibited by 
Synallaxis cinnamomeiis, brought, as it were, to perfec- 
tion : the toes are very slender, the inner one consider- 
ably the shortest, and the hinder one again so lengthened 
that it equals that of the middle: all the claws are 
large, very slender, and acute, but while those in front 
are greatly curved, that behind is much less so; its 
great length, however, added to the general character of 
t genera of the Scamnrrs, Tenuirostres^ and Fissirostres are equi- 
valent to the .sub-genera of the Insessores. ^ 
f Ihe typical si>ecics are Sy. Caniceps and Itujiceps. See Appendix. 
