Page:Encyclopædia Britannica, Ninth Edition, v. 3.djvu/735

] angle either rounded or obtuse-angled. The post-palatine region is bevelled off remarkably; but in Picumnus minutus, the lips of this part are greatly developed, as in the lower Passerines of South America; but in them this marked region appears to be always ossified directly from the main bone, whilst in Picumnus it is a separate ossifica tion a perfectly unique thing, as far as the writer s know ledge goes. The broad main part of the palatine suddenly narrows at its first third, the remaining two-thirds being the long splintery prepalatine, opposite the beginning of which the inner lip runs into an &quot;inter-palatine spike (i.pa.) The ethmo-palatine procc ;ses are extremely long in the nestling of Yunx, and very short in that of Picus minor (e.pa.) They are the free anterior ends of that ascending plate which lies under the parasphenoidal rostrum. These plates are united by a cartilaginous commissure, dagger- shaped, which ossifies as the most marked medio-palatine (m.pa.) seen in the class. The prepalatine band passes between the dentary and palatine spurs of the premaxillary (px.), as in the adult fowl. Oddly enough, th?y run on the inner side of the palatal process of the premaxillary in most of the j&amp;gt;ji.thognathce. This is an after-modification, for in the young of Struthio camelus and Gallus domesticus the fore-end of the one and the hinder end of the other process are broad, and the two unite by suture. In the higher birds the processes overlap on either side, but orderly as to natural groups. The free end of the pre maxillary palatine process looks backward to the free inter-palatine spur in the young (fig. 27) ; but in old birds, as may well be seen in Gecinus viridis, Picus analis, and P. major, these parts are formed into delicate bridges of bone, which also are thrown along to the ethnic-palatines. This is done by the vomerine series. The &quot; septo-maxil- laries &quot; are not single conchoidal plates of bone, as in the Snake and Lizard ; but are broken up into grains, which melt into each other again. Even the vomer itself is double on each side in Gecinus viridis, whilst in Htmilo- phns fulvus there are three septo-maxillaries on the left side and five on the right. These ossicles lie on the inner side of the palatines, and are normally connected behind by means of the vomer to the ethmo-palatine ; where normal ornithic ankylosis takes place in adult birds, there these curious length-wise bridges are formed. Yet this is only part of their complexity, for median septo-maxillaries appear, two of them in Gecimis, and these are found in the substance of long, right and left, labial cartilages. These do not ossify in Hemilophus, but unite at the mid-line ; in Gecinus they overlap largely to gain the mid-line. In the same species, to add to the complexity, a large shell of bone, from the inturned alinasal icall, becomes more or less free of its own origin, and unites to the vomerine series. All this has been seen and explained by writing and by figures. {{ti|1em|The maxillo-palatine processes scarcely grow inwards at all in Picumnus ; in Yunx they are rather larger; larger still in Picus minor (fig. 27, inx.}).) ^Yhere they are largest, as in Gecimis, they just rest upon the outer edge of the palatines, covering nearly half their width. In all, the under face of the maxillary has an open pneumatic space at this part. But, as if to fill up that which was wanting, a separate palatine plate appears on the inner edge of the maxillary further forward, only on the left side, however (fig. 27, p.mx.} This is a semi-oval wedge of bone, and has its symmetrical counterparts in several families of the Coraeomorphce, viz., Emberiza, Cardinalis, &c.}} These birds are saurognathous in other respects, e.g., their nasal labyrinth is unusually simple. The &quot; inferior turbinal,&quot; which has three coils in Rhea and Tinamus, and two in most birds, is in Gecinus merely bi-alate ; in Yunx it makes less than a single turn, whilst the alinasal turbinal of that bird has two turns, and that of Gecinus one. Gecinus is in all respects the most specialized, Picumnus the most embryonic, and Yunx the most passerine of the Celeomorphce. Also, in Gecinus the nasal labyrinth is most ossified, and in Yunx least. In Gecinus the &quot; columella auris &quot; has two supra-stapedial spurs and two infra-stapedial bands, which have united with the tongue- shaped stylo-hyal : this has in it a bony centre. The small cerato-hyals early coalesce into one arrowhead- shaped bone, and then comes a very long, highly ossified, and elastic basi-hyal, with no uro-hyal behind it. Joined to this are a pair of lower thyro-hyals, half its length ; but the upper pieces are four times the length of the lower, and they, passing first down the sides of the upper part of the neck, again turn gently upwards and forwards, plough ing themselves a furrow on the skull top, and deflecting gently to the right nasal roof, wnere they end.

All these things being considered, it will seem contra dictory now to assert the great uniformity of the skulls of Birds, and indeed of the Birds themselves. Yet so it is ; and the countless modifications that offer themselves for observation are gentle in the extreme. One form often is seen to pass into another by almost insensible gradations. One thing is certain, namely, that an anatomist not familiar with this class, and coming to its study fresh from the Reptiles, would find himself at fault at every turn ; for he would see changes altogether as great as if he had passed from the Helminthoid types, and from mere larvae and pupce of the Insects to the (to him suppcsably) unthought-of imagines that spring from those low and worm-like stages. In the rest of the Birds organization abundant evidence of the same specialization will be seen. The mind fails to desire more beauty or to contemplate more exquisite adaptations. An almost infinite variety of Vertebrate life is to be found in this class. Of its members some dig and bury their germs, which rise again in full plumage, whilst others watch and incessantly feed their tender brood in the shady covert or &quot; on the crags of the rock and the strong place.&quot; In locomotion some walk, others run, or they may wade, swim, plunge, or dive, whilst most of them &quot; fly in the open firmament of heaven.&quot;

.

The spinal column of birds contains numerous and well- ossified vertebras, a considerable number of which (more than six) are ankylosed together to form a sacrum. Of the vertebrae which enter into the composition of this com plex bone, however, not more than from three to five can be regarded as the homologues of the sacral vertebras of a Crocodilian or Lacertilian Eeptile. The rest are borrowed, in front, from the lumbar and dorsal regions ; behind, 