﻿114 ON THE CLASSIFICATION OF BIRDS. 



to the relative length of the tarsus, it is the form and 

 disposition of these scales which supply us with the best 

 discriminative characters taken from this part of the 

 foot. As no writer has yet given this subject the attention 

 it deserves, we shall here endeavour to elucidate it. The 

 generality of naked footed birds have the tarsus protected 

 by three series of scales, each of which is frequently of 

 a peculiar form. The first series is in front ; the second 

 occupy the two sides, and the third is at the back of the 

 leg. The front scales are called the anterior, and are 

 either composed of one or of several pieces. When the an- 

 terior scale is simple, or in one piece, it extends from the 

 front of the knee to the articulation of the hinder toe; and 

 its external surface, consequently, is very smooth. The 

 next deviation from this is seen in the sparrow-hawks, 

 where the tarsus is still very smooth, but there are slight 

 transverse divisions, which, upon a close inspection, seem 

 to be rather beneath than upon the surface; for they 

 are imperceptible to the touch. The next modification 

 is seen in these transverse divisions being, in some de- 

 gree, imbricate; that is, the edge of one lying over the 

 edge of the next: this is the general appearance of the 

 anterior scales in most birds, the number being variable 

 in the groups, though not in the individuals ; in most 

 of the small perchers the anterior scales are five or six, 

 the longest being in the middle of the tarsus, and the 

 smallest at its two extremities. Wading and aquatic 

 birds have the anterior transverse scales very narrrow, and 

 numerous. Tracing this modification onward, we find 

 that in some of the falcons the transverse scales begin to 

 be of unequal sizes, — next a few of them are divided, 

 as if to break the regular series, until, in the Falco 

 spar ver his, and its allies, the whole of the anterior scales, 

 which would otherwise be transverse, are divided by a 

 suture down the middle of the front into two sets : this 

 prepares us for a new pattern of scales, which we term 

 angulated or hexagonal, because the sutures of these 

 scales, or the lines by which they are connected, often 

 appear irregularly angulated. This latter form is more 

 especially found in the Rasorial birds, and the different 



