NEOTROPICAL REGION. j BIRDS 743 out of the Australian Region, and the Edentata, an Order which, though found also in Africa and India, attains in South America the summit of its development in variety and number of forms ; and we cannot adduce any examples of Orders or Suborders from the Class Aves, the circum stances of which will exactly match those of these three al groups of Mammalia. The nearest approach, perhaps, is
- ter .- made in one way by the South- American Ratite birds, of
ts which one entire group, consisting of at most three species (Rkeidffi), is peculiar to the region, and thus to some extent parallels the case of the Pedimana ; but while these last also invade the Nearctic Region, the former are not even spread over the whole of continental South America, being limited to its colder portion. Moreover, so far as Orders have been generally understood and accepted by ornithologists among Carinate Birds, there is no one of wide range which can compare with the overwhelming development of the Eden tates in the Neotropical Region. On the other hand, it must be observed that the Region claims all the Tinamous (Tina- midce) the Dromceognathoe of Professor Huxley which, if we were to follow his arrangement established on palatal characters, it would seem necessary to regard as the equivalent of an Order ; and also a single very remarkable form (Opisthocomus}, which he has satisfactorily shown to be so unlike every other that it can only be conveniently classed by itself. 1 Of these forms the Tinamidce certainly, and Opisthocomus probably, are of comparatively low de velopmental rank, in that respect resembling certain char acteristic Australian groups ; but the similarity between the avifaunas of the two Regions seems to be further borne out by the same fact being observable of other South- American families, forming what may be called the lower Suborders 2 of Passeres, to which the names of Oligomyod<x and Tracheophonce have been attached, and these, if not altogether originating in the Neotropical Region, are with out doubt therein most abundantly produced. The signi ficance of this fact is enhanced when we remember that, as has been said before, to consider rightly the problem of the distribution of birds, we must in the main rely on the Passeres, as affording on the whole the surest ground for cur investigations. Now, taking the latest, nay, the only, complete list of Neotropical birds that published by Messrs Sclater and Salvin 3 in 1873, we shall see that there are 8 Passerine families peculiar to the Region, of which 3 belong to the Tracheophonce, 4 to the Oligomyodce, and 1 only to the Polymyodce or Oscines. Or, if we look to the entire number of species given in that work as inhabiting the Region, we find it to be 3565. Of these, 1997, or a good deal more than half, belong to the Order Passeres a large proportion truly, but one that (from other causes not germane to our present investigation, and therefore to be just now disregarded) need not especially excite our wonder. But the characteristic nature of the avifauna of the Region is more clearly brought out when 1 To recognize these Orders, Crypturi and Opisthocomi, however, it becomes logically necessary to recognize many other groups in like manner, and thus to raise the number of Orders in the whole Class to at least two dozen, or nearly four times as many as most ornithologists have been usually willing to admit, a proceeding which naturally lowers the differential standard, and renders a comparison between "Orders" of Aves and "Orders" of Mammalia or Reptilia almost impossible. 2 The term "Suborder" should very possibly not be used here, at least in a technical sense. The Passeres seem to be properly divisible into two great groups one containing the genus Menura, the other all the rest, except most likely A trichia, which there is some reason to suppose may be found to form a third group. Whenever these groups shall receive names, they ought to be regarded as Suborders, but in the meantime, with this explanation, perhaps no harm will follow from calling the sections Polymyodce (the Oscines of some writers), Oligomyodce, and Tracheophonce " Suborders." 3 Nomenclator Avium Neotropicalium, &c., Auctoribus P. L. Sclater et, 0. Salvin. Londini : 1S/3. we learn that of the 1997 species just mentioned, 1070 only belong to the higher Suborder (Polymyodce), leaving 927 to the two lower Suborders (Oliyomyodw and Traclieo- phonai) ; or to speak in round numbers, out of 2000 species of the highest Order of birds, a little more than one-half belong to its highest section, while nearly one-half belong to its two lower sections. This is a state of things which exists nowhere else on the globe ; for, except in Australia, where a few but uncertain number of purely indigenous and peculiar non-polymyodous Passeres are found, and in the Nearctic Region whither one family of Oligomyodce has evidently been led by the geographical continuity of its soil with that of the Neotropical Region, such forms do not occur elsewhere. Accordingly their disproportionate prevalence in South America and its neighbouring lands points unerringly to the lower rank of the ornis of the region as a whole, and therefore to the propriety of taking it next in order to that of the Australian Region, the general fauna of which is admittedly the lowest in the world. It is believed that much the same result would follow from a similar examination of other Orders, especially the Picarice; and Professor Huxley has urged with his wonted perspicuity the alliance of the two Regions just named, basing his opinion in great measure on the evidence afforded by the two sections into which the true Gallince are divisible, the Peristeropodes and the Alectoropodes, the former composed of the families Megapodiidtx, almost wholly Australian, and the Cracidce, entirely Neotropical, but citing also other weighty evidence in favour of his conclusion. 4 Leaving, however, this matter as in some degree hypo thetical, though its probability can hardly be denied, we have as genera, families, or perhaps even larger groups a great many very remarkable forms which are characteristic of or peculiar to the Neotropical Region in part, if not as a whole. Of families we find 23, or maybe more, absolutely restricted thereto, besides at least 8 which, being peculiar to the New World, extend their range into the Nearctic Region, but are there so feebly developed that their origin may be safely ascribed to the southern portion of America. First in point of importance comes the extra ordinarily beautiful family of Humming-birds (Trocliilidce) , with nearly 120 genera (of which only 5 occur in the Nearctic Region), and more than 400 species. Then the Tyrants (Tyrannidai) , with more than 70 genera (8 of which range into the northern Region), and over 300 species. To these follow the Tanagers (Tanagridce), with upwards of 40 genera (only 1 of which crosses the border), and about 300 species ; the Piculules (Dendrocolaptidai), with as many genera, and over 200 species; the Ant- Thrushes (Formicariidai), with more than 30 genera, and nearly 200 species ; together with other groups which, if not so large as those just named, are yet just as well defined, and possibly more significant, namely, the Tapaculos (Ptero- ptockidce), the Toucans (Rhamphastidce), the Jacamars (Gal- bulidce), the Motmots (Momotidce), the Todies (Todidce), the Trumpeters (Psophiidcv), and the Screamers (Pala- medeidce) ; besides such isolated forms as the Seriema (Cariama) and the Sun-Bittern (Eurypyga}. Having thus briefly indicated some of the chief charac teristic and for the most part generally distributed forms of the Neotropical avifauna, we have next to consider the separation of the Region into Subregions and provinces. Herein we find far greater difficulty than we had to en counter in treating of the preceding (the Australian) Region, the geographical peculiarities of which marvellously lend themselves to its comparatively easy partition, while the isolation of its several portions contributes in an extraor- 4 Proceedings of the Zoological Society, 1868, pp. 294-319. Ornithic develop inent co: pnrative low. Charact istic far lies. Division into Sul
regions.