STRIGIN^. 



twelfths high, the ear three-twelfths and a half in dia- 

 meter, its inner aperture two-twelfths and three-quai- 

 ters. Thus, even the Thrushes have ears nearly as 

 large as those of the Hawk- Owls, and the Creeper and 

 Wren equal the Eagle- Owl in the relative size of their 

 auricular aperture. 



In some species of owl, the external aperture of 

 the ear is not much larger in proportion to the size of 

 the head than in the Circi as above represented ; but 

 in others it is of enormous size, and extends from the 

 base of the lower mandible to over the eye. The va- 

 rious gradations will be explained in the following em- 

 pirical generic characters. 



It may be proper to mention here, that the birds of 

 the first three genera have no tufts of elongated fea- 

 thers on the head, whereas those of the last three are 

 furnished with those appendages, the use of which is 

 one of the many mysteries. 



