422 Mr. N. A. Vigors om 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 

 the}?^ 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. lUiger alludes to some 

 Brazilian Falconidce with long tarsi, which do not seem to have 

 met with much attention, or to have been very accurately de- 

 scribed. These may perhaps be found to fill up part of the 

 vacancy which at present exists in our series of affinity. But 

 ail this is mere conjecture ; and it is useless to hazard observa- 

 tions which only tend to expose the narrowness of our informa- 

 tion, 



