136 
ON THE CLASSIFICATION OF BIRDS. 
shorter than the tarsus. It is only, however, in the 
Australian genus Climacteris that this excessive deve- 
lopment of the 
posterior toe is 
at its maximum 
{fg- 73. a) : in 
thisgenus, owing 
to its enormous 
claw, the hinder 
far exceeds the 
length of the 
middle toe, and this latter is connected to the one 
that is external, nearly to the end of its first joint 
(6). To account for this extraordinary enlarge- 
ment of the toes in all the preceding birds, it must 
be remembered 
that their faculty 
of climbing is 
entirely derived 
from thesemem- 
bers ; they re- 
ceive no assist- 
ance whatever 
from their tail, 
, , . „ . which is not 
only destitute of naked points, but of all rigidity 
less™^*^’ ** * of support, it becomes quite use- 
(123.) Let us now see what further variations occur 
in genera where some assistance must be derived 
from the tail, a fact we gather from the feathers nos 
sessing different degrees of rigidity, without their beinR 
absolutely stiff or terminating in naked points The 
genera whose tails are thus formed are Zeyinps (fig 74.) 
Anabates Dendromu, part of Synatla^u^ O^yrhynchm, 
and Buphaga. In the four first the tail, althou<»h pos 
sessing but a very slight degree of stiffness, is yet suf- 
ficiently firm to give some aid to the bird in chmbing 
