110 GENERAL ORNITHOLOGY. 



prong ; the skinny or horny sheath that stretches betwixt them is usually sunken below the 

 general level of the bill, especially in those birds whose prongs are long or widely separated ^ 

 this "ditch" is what we are about. It is called fossa when short and wide, with varying 

 depth; sulcus or groove when long and narrow; the former is well illustrated in Gallinaceous 

 birds ; the latter in nearly all wading birds and many swimmers. When the intermaxillary 

 prongs are soldered throughout, or are very short and close together, there is no (or no evident) 

 nasal depression, the nostrils then opening flush with the general surface. The 



Nostrils or Nares (Lat. pi. of naris, fig. 26, d), two in number, vary in position as fol- 

 lows : they are lateral, when on sides of upper mandible (almost always) ; culminal, when 

 together on the ridge (rare) ; superior or inferior when evidently above or below midway be- 

 twixt culmen and tomia; hasal, when at base of upper mandible; sub-basal when near it 

 (usual) ; median when at or near middle of upper mandible (frequent, as in Cranes, 

 Geese, etc.); terminal when beyond this (very rare; wo birds have nostrils at end of bill^ 

 except the Kiwis, ApterygidcB). 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; 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, when partitioned ofi" from each other, as in most birds ; but difi"ereut ornithologists 

 use these terms interchangeably, saying nares pervioe of nostrils which communicate with 

 each other, and nares impervice of nostrils shut off from each other by an internasal septum. 

 Principal shapes of nostrils may be thus exhibited: — a line, linear nostrils; a line variously 

 enlarged at either end, clavate, club-shaped, oblong, ovate nostrils ; a line, enlarged in the 

 middle, oval or elliptic nostrils ; this passing insensibly into a circle, round or circular nostrils ; 

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

 a few; almost never directly transverse (up and down). Rounded nostrils may have a raised 

 border or rim ; when this is prolonged they become tubular, as in the Goatsucker family and 

 all Petrels. Usually, nostrils are defined entirely by the substance surrounding them ; as a 

 cere, in Hawks, Owls, Parrots; softish skin, in a Pigeon, Plover, or Snipe, and much swollen 

 in the first named of these birds ; or horn, in most birds ; but often their contour is partly 

 formed by a special development, somewhat distinct either in form or texture, called the nasal 

 scale, or operculum. Generally, it forms a sort of overhanging arch or portico, as well shown 

 in Gallinaceous birds, among Wrens, etc A curious case of this is seen in the European 

 Wryneck {lynx torquiUa), where the scale floors instead of roofing the nostrils. In the sin- 

 gular Kagu {Rhinochetus jubatus), the operculum forms a large movable scroll, apparently 

 capable of closing the aperture. The nostrils also vary in being feathered or naked, the nasal 

 fossa being a place where frontal feathers are apt to run out in paired points (called antice), 

 embracing a small porti<m of the culmen (called mesorhinium) . Such extension of feathers may 

 completely fill and hide the fossa, as in Grouse and Ptarmigan ; but it oftener runs for a varying 

 distance toward, or above and beyond, the nostrils, as in Hummingbirds ; 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 feathered in varying degree, they are still open to 

 view; another condition is, their being covered and hidden by m.odified feathers not growing 

 on the bill itself, but on the forehead. These are usually bristly (setaceous), and form two 

 tufts, close-pressed and directed forward, as is perfectly shown in a Crow ; or, the feathers 

 may be less modified in texture, and form either two tufts, one over each nostril, or a single 

 ruff, embracing the whole base of the upper mandible, as in Nuthatches, Titmice, Red-polls, 

 Snow Buntings, and many other northern Fringillida;. Bristles or feathers tlius growing for- 

 ward are called retrorse (Lat. retrorsum, backward ; here used in the sense of in an opposite 

 direction from the lay of the general plumage ; but they should properly be called antrorse,. 



