Page:Encyclopædia Britannica, Ninth Edition, v. 3.djvu/729

distal third, and the lower is mainly bony; their basal

piece is largely soft behind (fig. 15, e.br., e.br., b.br.).

FIG. 22. Auditory "coutmeii.i" of

? st., stapes; m.tt., medio-stapcdial bar; s.st., super-stapedial; e.st., extra-stapedial; i.st., infra-stape- dial ; the end of this latter pro cess is the stylo-hyal, often more dilated than in this specimen ; /., funestra in extra-stapedial plate.

The skull of the Fowl, and of the Alectoromorphce generally, differs in certain re spects from that of other Schizognathoe. In the Gallinacece, as in the desmognathous Rapaces, the vomer is single ; in Pigeons and Sand-Grouse it is absent in all the others with open palates it is composed of two halves soldered more or less together. Some of the Schlzo- quatlvx possess an " os uncina- tum " as the Albatross and the Gull a bone to be described Hereafter ; and others possess a pair of bones attached to the double vomer, namely, the " septo-maxillaries," known in Reptiles as the so-called "inferior turbinals." These bones, very ^ ^^ small in all Birds, have been found by Mr Parker at the top and the bottom, as it were, of the scMzognafclioua series; that is, in the Humming-bird (Pata- f/ona, yiyas), and in the Kagu (Rhinochetus jiibatus). The latter is a Gruine bird, lying on the margin of the group towards the Night-Herons, whilst the Humming birds are certainly amongst the most specialized types. All the Schizo- gnathce, except the Fowl tribe, have meso-pterygoids." In certain Schizo- gnathce there is an " inferior labial " on the edge of the mandible, namely, in the Rcdlidae (?- f j., Fulica air a and Gallinula chloropus). These were found by the writer many years ago. Upper labials have not as yet turned up in these types, although they have been figured carefully in the Rhea (Phil. Trans., 18G6, plate 10, fig. 14, on each side of r.b.s., close under the inferior turbinal i.t.), and the Rhea is a much lower type than the birds under notice. As in the Gallinaccce, the Schizognatkae generally have little development of the tympanic ring, but in jtEgialitis hiaticula there is one large and three or four lesser bones on each side ; they occur in Numenius arquata.

A full and adequate idea of the degree of the metamorphosis of a Vertebrate skull attained to in Birds can only be obtained by observation of what is to be seen in that of the higher arboreal types. But some of the Carinatce are half and they possess that low kind of skull which is called " Dromaeo- gnathous," best seen in Dromceus, the Emeu.^[1] This kind of skull once understood, the relation of that of the Fowl to that of types far above and far below it will be clearly seen ; for we must describe the Desmognathous, yEgithognathous, and Saurognathous varieties also.

FIG. 23.- "Os hyoides of

Strut lllOUS, adult Fotc!, tenth stage, X 1 j diameters, c.h . cernto- hyals (confluent) ; b.h., the so-called basi-hyal, an swering to the first basi- branchial of a Fish; b.br., basi branchial, or uro-hyal, answeiing to the rest of the basi-branchial series of a Fish ; c.br., e.br. to gether form the thyro- hyal, answering to the first cerato- and epi-branchiala of a Fish.

The Dromæognathous Type—Cranium of Tinamus variegatus.—Professor Huxley (Clas. of Birds, p. 425) says, " The Droniceognathous birds are represented by the single genus Tinamus, which (as Mr Parker has shown)^[2] has a completely struthious palate. In fact, the vomer is very broad, and in front unites with the maxillo-palatine plates, as in Dromceus, while behind it receives the posterior extremities of the palatines and anterior ends of the ptery goid bones, which thus are prevented, as in the Ratitoe, from entering into any extensive articu lation with the basi- sphenoidal rostrum. The basi - pterygoid processes spring from the body of the sphenoid [they are not segmented plates of cartilage attached to the parasphenoid, as in the true Carinatce (see above)], not from the rostrum, and they articu late with the pterygoid very near the distal or outer ends of the latter bones." In the Fowl, as we have just seen, the fore-end, or main part of the pterygoid, glides on the rostral plate. " The head of the quadrate bone is single, as in the Struthious Birds (Parker, I.e.)" To this we may add that the basi-tempo- rals are very feebly de veloped, as we find from examination of threeadult Species : - T. robust US. T. 1 . , m j . variegatUS, and 1. brasi- liensis Sive major.^[3]

part of the jugal bars and the quadrate

bones have been removed, r.b.s., fore-end O f parasphenoidal rostrum ; a.p., anterior pterygoid process (basl-pterygoid).

If Professor Huxley s description be compared with the accompanying figure (24) of the Tinamine skull this variety will be easily understood; the lettering is the same as in the figures of the Fowl s skull. For further details the reader is referred to Mr Parker s Memoirs above referred to, especially that on the Struthious types (Phil, Trans. 1866, plates 7-15).

The Desmognathous Type of Skull.—Thia kind of

skull occurs in such a variety of families that, notwith standing its importance to the morphologist, it is not^of so great a value to the zoologist. Nor indeed is it quite

equal to some of the groups in value, being due to a

---

1. ^ Phil Trans., 1306, plates 11-13.
2. A note is given below as follows : "On the Osteology of Gallin aceous Birds and Tinamous (Transactions of the Zoological Society, vol. v. 1864). Sundevall, however, had already said of f Tmamv t Rhynchotus, and Crypturus, Struthiones parvos referant. two are merely sub-genera of Tinamus. fin*
3. The writer hopes to show the development of this type of skull at some future time ; an embryo of Rhynchotus rufesccns is treasured np i for this purpose.