condition arising rather from an excess of osseous deposits than from any very striking metamorphosis of primordial elements. The skull of the Schizognathce easily runs, as it were, into this type ; whilst it crops up among such simple palates as those of the Fowl tribe, namely, in Crax globi- cera ; and Talegalla Lathami in old age is nearly desmo gnathous. So also on the Arucine borders of the Gruidce, the Kagu (Rhinochetus jubatus),[1] is almost a Night-Heron, and nearly desmognathous. In another region JVi/ctibius almost comes across to the gigantic Goatsuckers (Podargus) and the Oil-bird (Steatornis). (Bee Huxley, Clas. of Birds, p. 450.) In the paper just referred to (p. 453) the Desmo- gnathfe are thus described : " Those Cuvierian Grallce and Natatorcs which are not schizognathous, the Accipitres or Haptores, the Scansores [excluding the Picidce], and among the Passcres, most of the Fissirostres, all the Syndactyli, and Upupa, may be termed desmognathous. In these birds the vomer is often abortive, or so small that it dis appears from the skeleton. When it exists it is always slender, and tapers to a point anteriorly. The maxillo- palatines are united across the middle line, either directly or by intermediation of ossifications in the nasal septum. The posterior ends of the palatines and anterior ends of the pterygoids articulate directly with the rostrum, as in
the preceding division" [the Schizognathce.It is possible to make several important divisions in the kind and degree of desmognathism, as follows, namely—
a. Direct. In Falcons and Geese, the maxillo-pala- tines meet below at the mid-line, as in the Mammal. Two sub-varieties of this form occur, as in the Falcon, where the nasal septum is ankylosed to this hard palate, and in the Goose, where it remains free.
b. Indirect. This is very common, and is best seen in Eagles, Vultures, and Owls. The maxillo-palatines are ankylosed to the nasal septum, but are separated from each other by a chink.
c. Imperfectly direct. This is where the maxillo-palatine plates are united by harmony-suture and not by coalescence. Example Dicholophus cristatus. In young Falcons and Hawks the palate is at first indirect, is then imperfectly direct, and at last perfectly direct.
d. Imperfectly indirect. Here the maxillo-palatines are closely articulated with, and separated by, the " median septo-maxillary," but there is no ankylosis. Example Megalcvma asiatica.
e. Double Desmognathism. This is seen in Podargus, where the palatines as well as the maxillaries largely coalesce below; to a less extent this is seen also in the large r Hornbills (Bucerot). (Huxley, op. cit, pp. 445, 446, figs. 27, 28.)
f. Lastly, a compound form, in which the jegitho- gnathous skull becomes desmognathous, is seen in certain Coracomorphce (Gymnorhina, etc.), as will be shown below.
Professor Huxley s remark, that the vomer, " when it exists, is always slender, and tapers to a point anteriorly" (p. 435), is modified by a note he gives on the same page with regard to the broad emarginate vomer of Fulco. It has a similar, but not equal, enlargement in front in the Sacred Ibis (Thresciornis cethiopicus), and the knife-shaped vomer of the Duck tribe is often thick at the infero-anterior angle, as may be seen in (Edcmia nigra, Querquednla caudacuta, and Mareca penelope, but the vomer of the Chenomorplm is compound, and the antero-superior bone, whose lower angle in part is enlarged, is the median septo- maxillary : this may be seen in young Geese, and in the adult Crested Screamer (Chauna chavanci).
Here it will be necessary, in order to show the value of these types of skull, to insert Professor Huxley s masterly handling of the modifications of the desmognathous skull, and the groups in which it is present. It is open to us r however, to modify some statements of his and to superadd others, for the observation of which the present writer has- had much greater leisure, and the advantage of having dwelt long on the subject.
At page 4GO (op. cit.) we read : "Not fewer than seven groups of families appear to me to be clearly distinguish able in this subdivision, viz., the Chenomorphæ, Amphimorphæ, the Pelargomorphæ, the Dysporomorphæ, the Aetomorphæ, the Psittacomorphæ, and the Coccygomorphæ."
1. The Chenomorphæ.—"The lachrymal region is re markably long [save in the Screamer (Ch(nmaJ. The- basi-sphenoidal rostrum has oval, sessile, basi-pterygoid facets, like those of the Alectoromorplice. The flat and lamellar maxillo-palatines unite and form a bridge across the palate." Yet each of these plates has a large obliquely- ascending process ; the vomer lies on the groove formed by the union of the maxillo-palatines ; the more or less ossified septum, in old age, coalesces, by its outstanding processes, with those plates. The internal, but especially also the posterior angle of the mandible is largely developed, and so also is the transpalatine angle of the palatine. The glosso- hyal is very large and spatulate, and the thyro-hyals are flat and broad where the two unite. A remarkable struc ture is found in Ducks and Swans, namely, an ossicle on each side between the palatines, and stretching towards the maxillo-palatine plate: these bones arc the "inter- palatines ; " they tend to carry on the hard palate.
2. The Amphimorphæ.—"The genus Phcenicopterus is- so completely intermediate between the Anserine birds on the one side and the Storks and Herons on the other, that it can be ranged with neither of these groups, but must stand as the type of a division by itself. Thus the skull has the long lachrymo-nasal region, the basi-pterygoid facets [not so; see op. cit., p. 437, where they are truly- said to be rudimentary they are the merest prickles] r the prolonged and recurved angles of the mandibles, the laminated horny-sheath of the Chmomorphce ; but the maxillo-palatines are spongy [scarcely more so than in the Swan et hoc genus omne of the Anserines and Anatines], and the general structure of the rostrum is- quite similar to that found in the Storks and Herons. The nasals are thoroughly Anserine, having their crura separated by a rounded notch ; their palatines are quite Anserine, but are broader behind, being exactly like those of the Screamer; and yet they cut off the mcso-pterygoid, which coalesces with the palatine. This the Storks and their allies do ; the Clienomorplice do not. The pterygoids are like those of Thresciornis and Platalea, but the vomer is intermediate between that of the Goose and the Spoonbill". The orbital processes of the palatines, or "ethmo-pala- tines," run together as arched laminae from the body of the bone to the maxillo-palatine floor. They are very shell- like at first, and are attenuated in front. They coalesce together, and send down a bony keel of exquisite thinness in their hinder part. There is a part separate from the rest in front, just where they begin to narrow ; this is obviously the median septo-maxillary. Behind, where the palatines shoot below the rostrum of the sphenoid, each bone sends down a lamella ; each of these is bound to its fellow by fibrous tissue, and between these the vomer is wedged ; the thin plate belongs mutually to the palatines and the azygous vomer. In all the ordinary Chtnomorphce the ethmo- palatine spurs are long; in Phcenicoptervs enormously so ; in the Screamer they are very short. Hence the palato-vomerine structures of the Amphimorphce are Anserine, but much modified. So also in the hyoirJ apparatus; and the huge glosso-hyal is, although cartila ginous, the true counterpart of that of a Swan.
- ↑ See Trans. Zool, Soc., vol. vi. plates 91 and 92.
