Struthionidoe^i is not the strongest example of vvliat a Bird s skull may be. In a bird s-eye view we see the separate- ness of the nasals, the nasal processes of the premaxillaries, the fore-end of the frontals, the top of the ethmoid, and the lachrymals (fig. 19, n.px., n.,f., eth., L). Below (fig. 20), the premaxillaries still have sutures with the palatines and tnaxil- laries, and the latter has its jugal process, the jugal itself,
and the quadrato-jugal, all distinct (px., pa., mx.,j., q.j.) | An image should appear at this position in the text. A high-res raw scan of the page is available. To use it as-is, as a placeholder, edit this page and replace "{{missing image}}" with "{{raw image|Encyclopædia Britannica, Ninth Edition, v. 3.djvu/728}}". If it needs to be edited first (e.g. cropped or rotated), you can do so by clicking on the image and following the guidance provided. [Show image]  | |
Fig. 20. -The same skull, basal view. Here the slenderness of the upper facial
rods is in strong contrast with the massiveness of the skull itself. This skull is unusually schizognathous, the vomer (v.) being very small, and the maxillo- palatine processes (mx.p.) much aborted.
Moreover, the quadrate (q.), ptevygoid (pg.), the pala tines, and of necessity the mandible all these retain their joints, and traces of the union of the mandibular splints are long retained (fig. 21, d., ar.). So also do the elements of the hyoid arch, soon to be described, remain separate.
The whole cranial box, and all the inter-orbital region, have become one bone, whilst the various fontanelles are filled in. In the specimen which has been figured the inter-orbital fenestra (i.o.f.) is partly open, but it is often obliterated. Also we see that free periosteal bony growths have bridged over the temporal fossa, the post-frontal or " sphenotic " having met and coalesced with a zygomatic process of the squamosal (p.f., S q.). In the lower view we _ still see the notochordal dimple on the transverse occipital condyle (o.c. and the hinder margin of the basi- temporal plate is still traceable in front of the passages for the vagus and the internal carotid burrows (i.e.) This thick bony mass is totally ankylosed to the basi-sphenoidal region above. The prootic and alisphenoidal regions are land-marked below by the foramen ovale (5), which is some times, as in Fishes, divided into two by a bony bar. So free is the bony growth that the basi-temporal has coalesced with the temporal wing of the exoccipital (l.t., e.o.}, and in front of this bridge we see a number of passages, burrows, galleries, windows, <tc., leading above to the upper tym panic recess, in front to the anterior tympanic recess, below that to the eustachian opening, and on the middle of the inner face of the drum cavity a large hole which leads to the two fenestrse. The various bones of the palate are scarcely in the least changed in form or relative size since the time of hatching (fig. 20), and the copious growths of cartilage belonging to the nasal labyrinth are always soft ; these are not figured in the adult skull. There are, how ever, a few bony centres, the feeble representatives of the ossifications found amongst higher birds in this region. Thus, close in front of the broad wall-top of the ethmoid, in the substance of the septum nasi, there are two small ossicles, and on each side a similar bony point ; the rest remained unossified, all save a small part of the attached margin of the pars plana.
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FIG. 21. The same skull, side view, with the mnmlib .e a little dislocated. Here
the temporal fossa is bridged over by the junction of the post-frontal and squamo.al processes (p.f., s/j.) The processes of the mandible (i.a.p., p. a. p.) are characteristic of this type, and of the Anseriiue.
larger third post-oral arch, contain persistent cartilage. The elegant " columella auris " (fig. 22) is bony where ifc fits into the fenestra ovalis (st.), and the shaft, up to its rays (m.st.), also; but the short, notched supra-stapedial (s.st.), the tongue-shaped and fenestrate extra-stapedial (e.st.), and the slender, combined infra-stapedial and stylo- hyal (i.st.), all these are still cartilaginous.[1] The rest of the second post-oral is reduced to the arrowhead-shaped lingual bone, the coalesced and partly ossified cerato-hyals (c.h.), and an elegant ridged phalangiform basi-hyal (b.h.) The free end of the combined glossal piece is soft. There is no tympanic in the Fowl ; only in the Peafowl have we found one, and it is behind the membrane. The next arch, the thyro-hyal (first branchial in Ichthyopsida), is composed
of two almost equal rods ; the upper is only ossified in its- ↑ Sometimes, even in the Fowl, the infra-stapedial has a spatulata stylo-hyal at its free end (see Professor Huxley s figure, Proc. Zool. Soc., May 27 1869, p. 399, fig. 5 B, I. S.)
