BIRDS OP PREY. TYPICAL OWLS. 325 
different primary groups will repose upon the greater 
or less development and modification of these organs. 
Upon this principle we find that the divisions of the 
Strigid(B, made by modern ornithologists, can aU be re- 
ferred to one or other of the following groups : — 
1. Typical Owls, having the facial disk very large and 
complete, with large ears and (in general) an ample 
operculum j 2. Horned Owls, furnished with egrets, 
and a large facial disk, but having only small or mode- 
rate sized ears ; and 3. Diurnal or Hawk Owls, where 
the conch of the ear is comparatively small, and is 
destitute of an operculum : the head has no egrets, and 
the facial disk is imperfect or obsolete. The reader will 
be at no loss to perceive in tlie first the characters of 
the typical group ; in the second, the sub-typical ; and 
in the third the aberrant. Let us now consider each of 
these separately. 
(26T.) The STRiGiN^, or typical owls, are well re- 
presented by the common white species of this island. 
The head is uncommonly large, and the facaal disk of 
great circumference ; the extent of the latter is marked 
by a dense semicircle of rigid narrow feathers, form- 
ing a sort of collar, and of which the ends are turned, 
lying close upon each other in the manner of scales. 
The aperture of the ear, which is within this collar, is 
large, measuring in the brown owl more than an inch 
in length. This is protected by an operculum, which 
is sometimes much larger (as in Striw flammea) than 
the aperture, and sometimes nearly of the same size. 
These diflTerences, however, will not be regarded at pre- 
sent as generic. Owls of this group are eminently 
nocturnal, and their geographic distribution, as is usual 
in all pre-eminent types, is very wide ; the white owl, 
under slight variations of colour, having been found 
over all the temperate parts of America, in the sultry 
groves of India, and even in Australia. Without at- 
tempting, for the present, to arrange the sub-genera 
of this group in their natural order of succession *, we 
* This is a task of very peculiar difficulty, for it is frequently impossible 
Y 3 
