COMMON CROSSBILL. 21 



to direct and insert its cutting scoop underneath the seed, 

 and the food thus dislodged is transferred to the mouth ; 

 and it will be seen by a reference to the first figure, that 

 when the mandibles are separated laterally in this operation, 

 the bird has an uninterrupted view of the seed in the cavity 

 with the eye on that side to which the under mandible is 

 curved. 



" The degree of the lateral power," says Mr. Townson, 

 " is surprising, and they are fond of exercising it for mere 

 amusement ; they are, therefore, not a little mischievous. 

 My pets would often come to my table whilst I \vas writing, 

 and carry off my pencils, little chip boxes in which I oc- 

 casionally kept insects, and other similar objects, and tear 

 them to pieces in a minute. Their mode of operation is by 

 first pecking a little hole, in this they insert their bill, and 

 then split or tear the object by the lateral force. When I 

 treated them, as I often did, with almonds in their shells, 

 they got at the kernel in the same manner ; first pecking a 

 hole in the shell, and then enlarging it by wrenching off 

 pieces by the lateral power." 



During a series of observations on the habits and struc- 

 ture of British Birds, I have never met with a more interest- 

 ing, or more beautiful example, of the adaptation of means 

 to an end, than is to be found in the beak, the tongue, and 

 their muscles, in the Crossbill. 



Explanation of the vignette : 



Fig. 1 . Head of the Crossbill, side view : a, temporal 

 muscle ; 6, great pyramidal muscle. 



2. Head viewed from below : c, c, pterygoid mus- 



cles ; d, d, graciles muscles. 



3. Head, side view : a, pterygoid process ; 6, os 



omoideum; c, os quadratum; d, d, os jugale. 



4. Head viewed from behind : a, right temporal 



muscle ; 6, great pyramidal muscle. 



