154 GENERAL ORNITHOLOGY part ii 



etc.); terminal when beyond this (very rare; probably there are 

 now no birds with nostrils at the end of the bill, except the 

 A'pteryx). The nostrils are pervious, when open, as in nearly all 

 birds ; impervious, when not visibly open, as among cormorants and 

 other birds of the same order ; they are perforate when there is no 

 septum (partition) between them, so that you can look through them 

 from one side of the bill to the other, as in the turkey-buzzard, 

 crane, etc.; imperforate Avhen partitioned off from each other, as in 

 most birds ; but different ornithologists use these terms interchange- 

 ably. The principal shapes of the nostrils may be thus exhibited : — 

 a line, linear nostrils ; a line variously enlarged at either end, 

 clavafe, cluh-shaped, oblong, ovate nostrils ; a line, enlarged in the 

 middle, oval or elliptic nostrils ; this passing insensibly into the 

 circle, round or circular nostrils ; and the various kinds of more or 

 less linear nostrils may be either longitudinal, as in most birds, or 

 oblique, as in a few; very seldom directly transverse (up and down). 

 Rounded nostrils may have a raised border or rim, ; when this is 

 prolonged they are called tubular, as in some of the goatsucker 

 family, and in all the petrels. Usually, the nostrils are defined 

 entirely by the substance surrounding them ; thus, of cere, in a 

 hawk ; of softish skin, in a pigeon, plover, or snipe ; or of horn, in 

 most birds ; but often their contour is partly formed by a special 

 development, somewhat distinct either in form or texture, and this 

 is called the nasal scale. Generally, it forms a sort of overhanging 

 arch or portico, as well shown in all the gallinaceous birds, among 

 the wrens, etc. A very curious case of this is seen in the wryneck 

 (Iijnx torquilla), where the scale forms the floor instead of the roof 

 of the nostrils. The nostrils also vary in heing feathered or naked ; 

 the nasal fossa being a place where the frontal feathers are apt to 

 run out in points (called antice), embracing the root of the culmen. 

 This extension may completely fill and hide the fossa, as in many 

 grouse and ptarmigan ; but it oftener runs for a varying distance 

 toward, or above and beyond, the nostrils ; sometimes similarly 

 below them, as in a chimney-swift ; and the nostrils may be densely 

 feathered when there is no evident fossa, as in an auk. When thus 

 truly feathered in varying degree, they are still open to view ; 

 another condition is, their being covered over and hidden by 

 modified feathers not growing on the bill itself, but on the forehead. 

 These are usually bristle-like (setaceous), and form two tufts, close- 

 pressed and directed forwards, as is perfectly shown in a crow ; or, 

 the feathers may be less modified in texture, and form either two 

 ttifts, one over each nostril, or a single ruff, embracing the whole 

 base of the upper mandible ; as in nuthatches, titmice, red-poll 

 linnets, snow -buntings, and many other northern Fringillidce. 

 Bristles or feathers thus growing forward are called retrorse (Lat. 



