The Carinatae are divided, according to the formation of the
palate, into four “Suborders,” and named (i.) Dromaeognathae,
(ii.) Schizognathae, (iii.) Desmognathae, and (iv.) Aegithognathae.[1]
The Dromaeognathae resemble the Ratitae, and especially the genus
Dromaeus, in their palatal structure, and are composed of the
Tinamous (q.v.). The Schizognathae include a great many of the
forms belonging to the Linnaean Orders Gallinae, Grallae and
Anseres. In them the vomer, however variable, always tapers to a
point anteriorly, while behind it includes the basisphenoidal rostrum
between the palatals; but neither these nor the pterygoids are
borne by its posterior divergent ends. The maxillo-palatals are
usually elongated and lamellar, uniting with the palatals, and,
bending backward along their inner edge, leave a cleft (whence the
name given to the “Suborder”) between the vomer and themselves.
In the Desmognathae, the vomer is either abortive or so small as to
disappear from the skeleton. When it exists it is always slender,
and tapers to a point anteriorly. The maxillo-palatals are bound
together (whence the name of the “Suborder”) across the middle
line, either directly or by the ossification of the nasal septum. The
posterior ends of the palatals and anterior of the pterygoids articulate
directly with the rostrum. The Aegithognathae, the fourth and last
of the “Suborders,” is characterized by a form of palate in some
respects intermediate between the two preceding. The vomer is
broad, abruptly truncated in front, and deeply cleft behind, so as
to embrace the rostrum of the sphenoid; the palatals have
produced postero-external angles; the maxillo-palatals are slender at
their origin, and extend obliquely inwards and forwards over the
palatals, ending beneath the vomer in expanded extremities, not
united either with one another or with the vomer, nor does the
latter unite with the nasal septum, though that is frequently
ossified.
The above abstract shows the general drift of this very remarkable contribution to ornithology, and it has to be added that for by far the greater number of his minor groups Huxley relied solely on the form of the palatal structure, the importance of which Dr Cornay had before urged, though to so little purpose. That the palatal structure must be taken into consideration by taxonomers as affording hints of some utility there can no longer be a doubt; but perhaps the characters drawn thence owed more of their worth to the extraordinary perspicuity with which they were presented by Huxley than to their own intrinsic value, and if the same power had been employed to elucidate in the same way other parts of the skeleton—say the bones of the sternal apparatus or even of the pelvic girdle—either set might have been made to appear quite as instructive and perhaps more so. Adventitious value would therefore seem to have been acquired by the bones of the palate through the fact that so great a master of the art of exposition selected them as fitting examples upon which to exercise his skill.[2] At the same time it must be stated this selection was not premeditated by Huxley, but forced itself upon him as his investigations proceeded.[3] In reply to some critical remarks (Ibis, 1868, pp. 85-96), chiefly aimed at showing the inexpediency of relying solely on one set of characters, especially when those afforded by the palatal bones were not, even within the limits of families, wholly diagnostic, the author (Ibis, 1868, pp. 357-362) announced a slight modification of his original scheme, by introducing three more groups into it, and concluded by indicating how its bearings upon the great question of “genetic classification” might be represented so far as the different groups of Carinatae are concerned:—
Huxley regarded the above scheme as nearly representing the affinities of the various Carinate groups—the great difficulty being to determine the relations to the rest of the Coccygomorphae, Psittacomorphae and Aegithognathae, which he indicated “only in the most doubtful and hypothetic fashion.” Almost simultaneously with this he expounded more particularly before the Zoological Society, in whose Proceedings (1868, pp. 294-319) his results were soon after published, the groups of which he believed the Alectoromorphae to be composed and the relations to them of some outlying forms usually regarded as Gallinaceous, the Turnicidae and Pteroclidae, as well as the singular hoactzin, for all three of which he had to institute new groups—the last forming the sole representative of his Heteromorphae. More than this, he entered upon their geographical distribution, the facts of which important subject are here, almost for the first time, since the attempt of Blyth already mentioned,[4] brought to bear practically on classification.
Here we must mention the intimate connexion between classification and geographical distribution as revealed by the A. Milne-Edwards. palaeontological researches of Alphonse Milne-Edwards, whose magnificent Oiseaux Fossiles de la France began to appear in 1867, and was completed in 1871—the more so, since the exigencies of his undertaking compelled him to use materials that had been almost wholly neglected by other investigators. A large proportion of the fossil remains, the determination and description of which was his object, were what are very commonly called the “long bones,” that is to say, those of the limbs. The recognition of these, minute and fragmentary as many were, and the referring them to their proper place, rendered necessary an attentive study of the comparative osteology and myology of birds in general, that of the “long bones,” whose sole characters were often a few muscular ridges or depressions, being especially obligatory. Hence it became manifest that a very respectable classification can be found in which characters drawn from these bones play a rather important part. Limited by circumstances as is that followed by Milne-Edwards, the details of his arrangement do not require setting forth here. It is enough to point out that we have in his work another proof of the multiplicity of the factors which must be taken into consideration by the systematists, and another proof of the fallacy of trusting to one set of characters alone. But this is not the only way in which the author has rendered service to the advanced student of ornithology. The unlookedfor discovery in France of remains which he has referred to, forms now existing it is true, but existing only in countries far removed from Europe, forms such as Collocalia, Leptosomus, Psittacus, Serpentarius and Trogon, is perhaps even more suggestive than the finding that France was once inhabited by forms that are wholly extinct, of which in the older formations there is abundance. Unfortunately none of these, however, can be compared for singularity with Archaeopteryx or with some American fossil forms next to be noticed, for their particular
- ↑ These names are compounded respectively of Dromaeus, the generic name applied to the emeu, σχίζα, a split or cleft, δέσμα, a bond or tying, αἴγιθος, a finch, and, in each case, γνάθος, a jaw.
- ↑ The notion of the superiority of the palatal bones to all others for purposes of classification has pleased many persons, from the fact that these bones are not infrequently retained in the dried skins of birds sent home by collectors in foreign countries, and are therefore available for study, while such bones as the sternum and pelvis are rarely preserved. The common practice of ordinary collectors, until at least very recently, has been tersely described as being to “shoot a bird, take off its skin, and throw away its characters.”
- ↑ Perhaps this may be partially explained by the fact that the Museum of the College of Surgeons, in which these investigations were chiefly carried on, like most other museums of the time, contained a much larger series of the heads of birds than of their entire skeletons, or of any other portion of the skeleton. Consequently the materials available for the comparison of different forms consisted in great part of heads only.
- ↑ It is true that from the time of Buffon, though he scorned any regular classification, geographical distribution had been occasionally held to have something to do with systematic arrangement; but the way in which the two were related was never clearly put forth, though people who could read between the lines might have guessed the secret from Darwin's Journal of Researches, as well as from his introduction to the Zoology of the “Beagle” Voyage.
