118 ON THE CLASSIFICATION OP BIROS. 
scales : and it may be remarked, generally, that they 
are almost obsolete in the perching order. The rasorial 
birds, on the contrary, possess them in the highest state 
of development. To ascertain this, let the student 
examine the leg of a common partridge : the anterior 
scales of this bird are large and transverse, but divided 
by an undulating line down the middle of the foot into 
two series : on each side of the leg arc placed the lateral 
scales, very small, of a lengthened oval shape, and oc- 
cupying but a narrow strip, altlwugh they are arranged 
in three series : following these are two rows of pos- 
terior scales, one on each side of the leg, divided in an 
obliquely transverse direction, and fully as large as those 
in front. There can be no doubt that a leg, thus 
strengthened and protected, possesses much more power 
than if its covering was less perfect, and this will be 
farther manifested upon examining the legs of the Bra- 
zilian partridges, forming the genus Crypturus { fig. 62.) : 
here the anterior scales are thin, with their .divisions 
finely, and even obscurely marked ; the lateral are almo.st 
obsolete, but the posterior, which are arranged trans- 
versely, are remarkably broad and strong, as if to com- 
pensate for the weakness of the others. Now, as the 
legs of this genus are obviously less robust than those 
of our partridge, although both live equally upon the 
ground, it would seem to follow that the posterior scales, 
above all the others, are more especially essential to 
terrestrial birds, and that it is for this reason we find 
them more pre- 
valent and more 
developed in the 
Rasores than in 
any other order. 
The strong and 
acute spurs and knots, with which so many of the feet of 
these birds are armed, are seated in the line of the poste- 
rior scales, and seem, in fact, but the excessive enlarge- 
ment of some one or two of them : this singular develope- 
ment of a spur may be traced in the young bird, when 
