1 2 INTRODUCTION. 



latcd); and next to the relative length of the tarsus, 

 the form and disposition of these scales supply us 

 with the best discriminative characters taken from 

 this part of the bird. 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. 



T\ie front scales, caWed also the anterior, are either 

 composed of one or several pieces. When the ante- 

 rior scale is simple, or composed of one piece, it 

 extends from the front of the knee as far as the 

 hinder toe, and its external surface is quite smooth. 

 Generally, however, this front plate is marked by 

 transverse divisions, or composed of pieces, which 

 sometimes overlap each other. In many birds, both 

 the front and sides of the tarsus are covered with 

 numerous small scales that do not touch each other, 

 but are so disposed that the interstices, or spaces 

 between them, resemble the lines of a net : such a 

 tarsus is said to be reticidated. 



The lateral scales of the tarsus are not alwaj^s 

 present; frequently their office is supplied by the 

 anterior scales, which are then extended round the 

 leg, so as nearly to envelop it. 



The posterior scales are very frequently wanting, 

 and when present seldom extend much below the 

 upper part of the tarsus. 



The Toes of birds, by their leading variations, 

 furnish the primary characters whereby the whole 

 class is divided into orders, and the subordinate 

 modifications of their structure indicate for the 

 most part natural groups. 



The great majority have four toes on each foot, 

 three of which are usually placed before, and one 

 (the liallux) behind. The exceptions to this number 

 of toes and to their disposition are comparatively 

 few. They will be noticed when speaking of the 

 particular races in which they exist. 



