THE ANATOMY OF BIRDS. — OSTEOLOGY. 161 



The Facial Bones proper is tlie Vomer. — By "facial bones," as distinguished from 

 " cranial " bones, is nieaut the entire bony scatfokliiig of the upper and lower jaws, aud of the 

 tougue, — parts developed in the pre-oral or maxillary, and first, second, and tliird post-oral, or 

 mandibular, hyoidean proper, aud branchial, arches. 



The Vomer (Lat. vomer, a ploughshare ; figs. 02, G.'3, 75 to 80, v) is considered, by those 

 whcj hold the vertebral theory of the skull, to be the body of the foremost (fourth from behind 



— the basioccipital, basisphenoid, and prcsphenoid beiug the CJther three) cranial vertebra. So 

 far from having any such morphological .significance, it is one of the late secondary bones, 

 developed, if at all, apart from the general make-uj) of the skull, as a special superadditiou 

 underlying the ethmoidal region, as the parasphenoid and basitemporal underlie the skull further 

 back. Its character is extremely variable in the class of birds, though usually constant in the 

 se\-eral natural divisions of the class, — a feet which confers high zcjological value upon this 

 anomalous bone. A vomer is a symmetrical mid-liue bone of the base of the skull, found if at 

 all at or near the end of the rostrum. It is originally double, i. e., of right and left paired 

 halves. These halves persist distinct in the woodpeckers, and are remote from each other, 

 one on each side of the mid-hne (fig. 80). The vomer is wanting entirely in the Columbine 

 birds, as the pigeons and some of their allies, as the sand grouse {Pterochtes ) and bush quails 

 {Hemipodes) of the old world, and in certain of the true Gallince. Its connections are various. 

 It may be borne free upon the end of the rostrum. It may be applied like a splint by a grcjoved 

 upper surface to the under side of the rostrum, and so fixed there ; or, in such situation, it may 

 glide along the rostrum according to the movements of the palatal parts with which it may 

 connect. Thus, in the ostrich (fig. In), it saddles tlie rostrum below, and is joined by the 

 maxiUo-palatines. Or, it may be united with sejjarate ossifications, the septo-maxillaries, 

 which in some birds bridge across the palate (fig. 80). The comnj(.iuest case is its deep 

 bifurcation behind (fig. 79), each fork uniting witli the palate bone of its own side, aud some- 

 times also with the pterygoid. Such is usually the fixture of the bone behind, aud it then rides 

 along as well as simply bestrides the rostrum. The anterior end of the vomer may be perfectly 

 free, projecting into the floor of the nasal chambers (figs. 03, 77), or the foi'e end may be 

 variously steadied or connected with maxillary processes (fig. 7S). When free in front, and 

 (iften when not, the vomer is a simple share-like plate, more or less expanded vertically, quite 

 tliin laterally, and " spiked," i. e., running forward to a point ; under these circumstances it may 

 or may not bifurcate behind, and be there attached to the palatines or not. But the commonest 

 case of vomer, shown by the great Passeriue group, Avhich comprise the majority of recent 

 birds, is different from this, the vomer being in front thickened, flattened and expanded laterally, 

 and connected with nasal cartilages and ossifications (alinasals aud turbinals). Such a vomer, 

 deeply cleft behind to join the palatals, is endlessly diversified in the configuration of its fore end, 

 which may be notched, lobed, clubbed, etc. The general case of such a vomer is indicated by 

 the expression " vomer truncate in front," as distinguished from the simidy pointed or "spiked" 

 vomer. (For farther details see description of the several patterns of palate-structure, beyond.) 



The Quadrate Bone (Lat. quadratus, squared; figs. 02; 03, n; CA, 0.5, 08, 69, 71, q; 

 75, Qu), with which we may begin the jaw-bones proper, is the susiwnsorium of the lower jaw, 



— the perfectly constant and characteristic bone by means of whicdi the mandible proper articu- 

 lates with the skull. Its rudiment is seen in the earliest embryos, at the corners of the pri- 

 mordial parachordal cartilages. It belongs to the mandibular (first post-oral) arch, of which it 

 is the proximal element. Its general morjihidogy has caused much dispute. From the fact 

 that in birds one of its functions is to support, in part, the tynqianum of the oar, it has been 

 identified with the tympanic bone of mammals, — that which in man forms the bony tube of the 

 external auditory meatus. The view now generally accepted is, that the bird's quadrate repre- 



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