﻿116 ON THE CLASSIFICATION OF BIRDS. 



American genus Thamnophilus (b), they are divided into 

 several distinct pieces ; the two last groups afford a strik- 



ing illustration of the regularity and constancy with which, 

 in some groups, the scales of the tarsi are constructed. 

 The American bush shrikes, and those of tropical Africa, 

 were united in the genus Thamnophilus, until we de- 

 tached the latter as a distinct genus, under the name of 

 Malaconotus. So closely, however, do these shrikes of 

 the two continents resemble each other in all but their 

 tarsi, that it is very difficult for an ordinary naturalist 

 to distinguish them otherwise than by their lateral scales. 

 Why such a marked and invariable distinction should 

 exist in the simple covering of the tarsi, between birds 

 so closely alike in all other parts of their general form 

 and structure, cannot possibly be explained. It is pro- 

 bable, however, that entire lateral scales give much more 

 strength to the muscles of the tarsus than would be 

 effected by a number of small pieces, and we, conse- 

 quently, find that the true shrikes, whose feet are ob- 

 viously more powerful than those of the American group, 

 have the scales entire ; and as this latter structure be- 

 longs also to the American M alaconoti, we may con- 

 clude that they are more rapacious than their American 



