Lastly, we come to the final order of the Neotropical Ornis in the shape of the Rheas, or the American representatives of the Ostrich-type of bird-life. The Rhea is, above all other birds, a most characteristic representative of the Avifauna of the Patagonian subregion. It is true that it ranges far north throughout the campos of Inner Brazil, where the outlying members have become developed into an almost distinct species or subspecies, _Rhea americana macrorhyncha_. But south of the Rio Negro of Patagonia another very distinct type of Rhea, almost subgenerically different, is met with and extends thence to the Straits of Magellan. _Rhea_ has also been lately ascertained to occur on the western side of the Andes in the Chilian province of Tarapaco; so that this fine form of bird-life is diffused nearly over the entire Patagonian subregion, and is well entitled to be termed one of the most characteristic features of the Patagonian Avifauna. In conclusion, therefore, we may sum up our present knowledge of the Argentine Avifauna somewhat as follows:-- The Argentine Avifauna comprises 434 species of birds, referable to 54 families and genera. All the twenty Orders of the Neotropical Avifauna have representatives within its boundaries, except the _Opisthocomi_ or Hoatzins, which are restricted to the Amazonian subregion. The most numerous families of the Argentine Avifauna are, among the Passeres, the Finches with 46 species, the Tyrants with 63 species, and the Wood-hewers with 46 species. Among the remaining Orders, the Diurnal Birds of Prey with 19 species, the Waterfowl with 22 species, the Rails with 13 species, the Snipes with 15 species, and the Tinamous with 8 species, are likewise well represented. Genera characteristic and proportionately numerous in species in the Argentine Avifauna are _Poospiza_ and _Phrygilus_ among the Finches, _Tænioptera_ and _Cnipolegus_ among the Tyrants, _Synallaxis_ among the Wood-hewers, _Fulica_ among the Rails, and _Nothura_ among the Tinamous. Less numerous in species, but highly characteristic forms of the Argentine Ornis, are _Thinocorus_, _Rhynchotis_, and _Rhea_. The following ten genera, mostly monotypic, are, so far as we know at present, restricted to the limits of the Argentine Avifauna or its immediate confines:--_Donacospiza_ and _Saltatricula_ (Fringillidæ); _Coryphistera_, _Anumbius_, _Limnornis_, and _Drymornis_ (Dendrocolaptidæ); _Rhinocrypta_, with two species (Pteroptochidæ); _Spiziapteryx_ (Falconidæ); _Chunga_ (Cariamidæ); and _Calodromas_ (Tinamidæ). ARGENTINE ORNITHOLOGY. Order I. PASSERES. Suborder I. _OSCINES._ Fam. I. TURDIDÆ, or THRUSHES.