SKELETON 



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considerable help in Taxonomy (Classification). It must suffice 

 here to refer for the names of the parts to the subjoined figure. 



The Bill, or Beak, is composed of an upper jaw or maxilla, 

 and an under jaw or mandible. From the figure it will he seen 

 that " maxilla " is not strictly the whole upper portion, though 

 the term is thus used for convenience, as is the plural "mandil^les" 

 for the two jaws when mentioned simultaneously. The " rliam- 

 photheca," or horny slieath, 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 



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Fig. 5. Skull of a Wild Duck {Anas hnscas), from the side, ag, Angular; rds, 

 alisphenoid ; ar, articular ; bt, iiasitemporal ; d, dentary ; en, external nostrils ; e.o, 

 exoccipital ; eth, ethmoid ; ft; frontal ; j, jugal ; Ic, lacrymal ; mx, maxilla ; mx.j), 

 maxillopalatine process ; n, nasal ; ja, parietal ; jjffi pterygoid ; ^j?, palatine ; fj.s, 

 presphenoid ; ^a-c, premaxilla ; q, quadrate ; q.j, quadratojugal ; s.ag, supra-angular ; 

 s.n, supraoccipital ; sq, squamosal ; t>/, tympanic cavity ; r, vomer ; //, forameu for 

 optic nerve ; V, for trigeminal. (From Wiedersheim, after Parker.) 



the Limicolac it varies extremely, producing a hard pickaxe, as 

 in the Oystercatcher, or a delicate sensory organ as in the Snipe 

 and Woodcock. The rhamphotheca at times has extraordinary 

 outgrowths, as in the Hornbills, Sheathbills, and elsewhere. In 

 the Accipitres, or Diurnal Birds of Prey, and most Fsittaci, the 

 base is soft and becomes a " cere," while the similar formation in 

 the Cohimhae is due to a swelling of the operculum or covering 

 of the nostrils. This operculum, moreover, may be leathery (coria- 

 ceous), as in the Charudriidae, Trochilidae and so forth, or rolled 

 up, as in Rhinochetus ; it may even result in a short soft tube, 

 as in Ccqorimulgus, or in the hard double tul)e which gives the 

 name of TuMnares to the Petrels. "Impervious" nostrils are those 

 with a septum, or division, between the nasal cavities, " pervious " 



