I SKELETON 1A 
considerable help in Taxonomy (Classification). It must suffice 
here to refer for the names of the parts to the subjoimed figure. 
The Bill, or Beak, is composed of an upper jaw or maxilla, 
and an under jaw or mandible. From the figure it will be seen 
that “maxilla” is not strictly the whole upper portion, though 
the term is thus used for convenience, as is the plural “mandibles” 
for the two jaws when mentioned simultaneously. The “ rham- 
photheeca,” or horny sheath, may be simple (undivided), or com- 
pound, that is, made of several distinct pieces. In the Anseres 
the covering is soft with a horny (corneous) tip or “nail”; in 
Fig. 5.—Skull of a Wild Duck (Anas boscas), from the side. ag, Angular; als, 
alisphenoid ; a7, articular ; bt, basitemporal ; d, dentary ; en, external nostrils ; e.0, 
exoccipital ; eth, ethmoid ; fr, frontal ; 7, jugal ; @c, lacrymal ; mx, maxilla ; mz.p, 
maxillopalatine process; 2, nasal; p, parietal; pg, pterygoid ; p/, palatine ; ps, 
presphenoid ; pa, premaxilla ; g, quadrate ; ¢.7, quadratojugal ; s.ag, supra-angular ; 
8.0, supraoccipital ; sq, squamosal ; ¢y, tympanic cavity ; v, vomer ; Z/, foramen for 
optic nerve ; V, for trigeminal. (From Wiedersheim, after Parker.) 
the Limicolae it varies extremely, producing a hard pickaxe, as 
in the Oystercatcher, or a delicate sensory organ as in the Snipe 
and Woodeock. The rhamphotheca at times has extraordinary 
-outgrowths, as in the Hornbills, Sheathbills, and elsewhere. In 
the Accipitres, or Diurnal Birds of Prey, and most Psitfaci, the 
base is soft and becomes a “cere,” while the similar formation in 
the Columbae is due to a swelling of the operculum or covering 
of the nostrils. This operculum, moreover, may be leathery (coria- 
ceous), as in the Charadriidae, Trochilidae and so forth, or rolled 
up, as in Rhinochetus ; it may even result in a short soft tube, 
as in Caprimulgus, or in the hard double tube which gives the 
name of Zubinares to the Petrels. “Impervious” nostrils are those 
with a septum, or division, between the nasal cavities, “ pervious ” 
