422 Mr. N. A. Vicors on the Natural Affinities 
a corresponding structure with that required by the moist places 
which form the ordinary resort of the Waders: and the Bird of 
Prey, that pursues its reptile food over the loose and unstable 
footing of the desert, seems to stand in need of a length of limb 
equal to that which is necessary for the Wader among the marshes. 
Other instances occur of an analogous provision of Nature. The 
Ostrich, whose chief abode is among the barren plains of the torrid 
zone, is endowed with a similar length of limb : and the Giraffe, 
that tallest work of the animal creation, is exclusively confined to 
the limits of the same sandy regions. While on this subject, it 
may also be observed that the legs of the Gypogeranus, although 
similar to those of the Waders, are not the same with them in 
structure. Those of the former bird are plumed, like the legs 
of the Raptores, as far as to the knee ; while in the Wading Birds 
. they are devoid of feathers: the dry nature of the sands not re- 
quiring the same nakedness of limb in the one group, which the 
moistness of the marshes renders necessary in the other. The 
genus Gypogeranus is at present composed but of one species, 
the well-known Secretary Vulture of the Cape. But judging from 
its structure and habits, and the adaptation of both to the arid 
nature of the plains which it frequents, it appears probable that 
some congeneric birds may exist in the hitherto impenetrable 
deserts of that vast continent, on the outskirts of which this soli- 
tary species is found. I have some doubts also whether a part of 
the raptorial birds which have been noticed in South America 
may not be allied to this genus. M. Illiger alludes to some 
. Brazilian Falconide with long tarsi, which do not seem to have 
met with much attention, or to have been very accurately de- 
scribed. 'lhese may perhaps be found to fill up part of the 
vacancy which at present exists in our series of affinity. But 
all this is mere conjecture; and it is useless to hazard observa- 
tions which only tend to expose the narrowness of our informa- 
tion, 
