BILL OF THE FINCH. 



189 



following figure of the common crossbill (Loxia cur- 

 virostra), which is of the natural size, and taken from 

 a dissection by Mr. Yarrel, to whom we are indebted 

 for the original and the best account of this curious 

 organ, and the mode of its action. 



Fig. 1. 



Fig. 2. 



Figure l,is a profile of the bill, with the skull and 

 the principal muscles. The one marked a, and situated 

 in the posterior part of the skull, is articulated behind 

 the centre of motion in the articulation of the jaw ; 

 and the "one marked b, extends before it as far forward 

 as the gape ; but these are assisted by other muscles. 



Figure 2 is an outline of the tongue, which is as 

 curious as the other parts of this feeding apparatus. 



It will be seen that both mandibles have a double 

 curvature ; the upper one is curved downwards and 

 the lower one upwards, and the one curves to the 

 right and the other to the left, so that the points cross 

 each other ; and Mr. Yarrel found them to be about 

 three-eighths of an inch apart when the bill was 

 closed at the basal part. In the figure the upper 

 mandible curves to the right and the under one to the 

 left ; but that arrangement is reversed in many of 

 the specimens. The side to which the mandibles 

 turn is thus not a specific character of the bird. 



