406 MANUAL OF ELEMENTARY ZOOLOGY 



formed by the union of mesethmoid with presphenoid and orbitosphenoid 

 elements to form a single plate of bone with a thickened ventral edge, 

 known as the rostrum, representing the blade of the parasphenoid. 

 The frontal sends downward a postorbital process. The lacrymal of 

 each side is a small, flat, curved bone, in front of and above the 

 orbit. In the olfactory region, the nasals are a pair of thin bones 

 in the roof, before the frontals. Their fore edges are deeply notched 

 for the nostrils. The vomers of the pigeon are vestigial. In the 

 common fowl they are represented by a slender median rod in front 

 of the rostrum. In the upper jaw, the palatines are a pair of slender 



pm. . 



•■*. OC. 



••' / sa. Eu. Affi\ "'S 

 pi. q. M. 



e. oo. 



Fig. 296. — The skull and some of the cervical vertebrae of a pigeon, 

 from the left side. 



d., Dentary ; Eu., Eustachian tube; e.oc, exoccipital ; f.r., fenestral recess ',Jr., 

 frontal; i.o.s., interorbital septum; lac., lacrymal; it., nasal ; par., parietal ; 

 pi., palatine; pm., premaxilla ; p.o.p., postorbital process of frontal; pt., 

 pterygoid; '/., quadrate; s.o.b., suborbital bar; s.oc, supraoccipital : set., 

 supra-angular; sq., squamosal; zy. , zygomatic process of the squamosal; /., 

 //., foramina for first two cranial nerves ; 1-3, first three cervical vertebrae. 



bars placed lengthwise in the roof of the mouth. From the hinder 

 end of each a short, stout pterygoid slopes outwards and back- 

 wards to join the quadrate, which is a strong, three-branched bone 

 articulated above with the squamosal, in front with the pterygoid, 

 and below with the lower jaw, whose suspensorium it forms. The 

 premaxilla of each side is a large, triradiate bone with the main part 

 directed forward and fused with its fellow to form the tip of the beak, 

 while two other processes pass back to join the two forward processes 

 of the nasal and thus enclose the nostril. The maxilla is a rod lying 

 inside the lower backward process of the premaxilla and projecting 

 backward beyond it. It gives off a plate of bone, the maxillopalatine 



