262 AFRICAN BRISTLE-BILL. 



It exhibits, in short, some of the typical characters 

 of each, and yet it is so equally connected to both, 

 that, for the present, we cannot determine to which 

 group it strictly belongs. To Dasycephala it is re- 

 lated by its lengthened, straight, and abruptly hooked 

 bill ; by a few incurved setaceous feathers and hairs 

 over the nostrils ; by the length of the tarsus and 

 of the middle toe ; and, by the great inequality be^ 

 tween the lateral toes. On the other hand, its 

 affinity to Trichophorus is shewn in its compressed 

 bill, the structure of its wings, and its geographic 

 station. It is usual to term a species possessing 

 such a union of characters as those just described, 

 a sub-genus, seeing that it does not precisely agree 

 with the definitions of any group hitherto named. 

 But this mode of proceeding may be carried too far ; 

 a little consideration will convince those who adopt 

 it, that in every natural group there must be oscu- 

 lent or aberrant species, without which every genus 

 would be isolated. If there is no approach in struc- 

 ture from the species of one group to the species of 

 another, there would not be that almost impercep- 

 tible gradation in nature which every one sees and 

 acknowledges. Some limits, therefore, must be put 

 to the creation of sub -genera, and every effort should 

 be made, in the first instance, to ascertain the 

 station of such forms among their congeners, and 

 this can only be done by extensive analysis. In the 

 present instance Dasycephala, according to the views 

 we have elsewhere published, is itself a sub-genus, 

 and such also is Trichophorus; it consequently 



