116 
ON THE CLASSIFICATION OP BIRDS. 
Arnerican genus Thamnophilus (h), 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 Thamnophilm, 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 aU hut 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 aU other parts of their general form 
and structure, cannot possibly be explained. It is pro- 
bable, however, that entire lateral scales give much more 
strengtli to the muscles of the tarsus than would be 
effected by a number of small pieces, and we, conse- 
quently, fiud 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 Mofeconoti, we may con- 
clude that they are more rapacious than their American 
