GEOGRAPHICAL DISTRIBUTION 323 



MORPH^. Both the Dromseognatlise and Heteromorphx are indubit- 

 ably of low developmental rank; in that respect, though in no 

 other, resembling certain Australian and New-Zealand groups ; but 

 the similarity between the Avifaunas of the three Regions composing 

 his Notogxa seems to be further borne out by the same fact being 

 observable in other South -American Families forming the lower 

 sections or suborders of Passeres, to which the names of Oligo- ^ , ^ 

 MYOD^ and Tracheophon^ have been applied — the Neotropical y- ^^^^^■''^ 

 Region haying a complete monopoly of the latter and a large pro- 

 portion of the former,^ according to our present knowledge. Of 

 the species of Passeres, belonging to the Region, we find that a little 

 more than one-half have to be classed under the highest sections of 

 that Order, while nearly one-half must be ranked under its two lowest 

 sections.^ This is a state of things that exists nowhere else, and it 

 is believed that much the same result would appear from a close 

 scrutiny of other Orders, especially of the Picarix. But more than 

 this, if we examine the true Passeres we find similar indications. 

 Their highest group, the Corvidse, is only just represented in the 

 northern portion by its highest genus Corvus, and even its lower forms, 

 belonging to the subfamily Garrulinm (Jay), only occur in parts of the 

 rest : the Fringillidgs though inhabiting the Region are vastly out- 

 numbered by the Tanagridx, and the Mniotiltidse occupy the position 

 elsewhere taken by the Sylviidse. 



Leaving, however, this question as in some degree hypothetical, 

 though its probability can hardly be denied, we have as genera, 

 Families, or even larger groups, a great many remarkable forms 

 that are characteristic of or peculiar to the Neotropical Region in 

 part if not as a whole. Of Families there are more than a score 

 absolutely restricted to it, beside some half-dozen which, being 

 peculiar to the New World, extend their range into the Nearctic 

 area, but are there so feebly develoj^ed that wherever they may 

 have originated in bygone ages, they may be safely ascribed now 

 to South America. First in point of numbers come the TrochiUdse 

 (Humming-bird) with, according to some systematists, nearly 150 

 genera, of which perhaps only 3 occur in the Nearctic area. 

 Then the Tyrannidse (King-BIRD) with above 70 genera, yet scarcely 

 more than 10 ranging into the Holarctic Region. To these follow 

 the Tanagridm (Tanager) with 40 genera, only 1 of which crosses 

 the border ; and, in addition to those before mentioned the various 

 Families of Conopopliagidx, Cotingidm, Dendrocolaptidse, Formicariidx, 

 Furnariidse (Oven-bird), Pipridse (Manakin), and Pteroptochidse 



^ The exceptions are Tyrannidx, which occur in comparatively small pro- 

 portion in North America, Pittidee, Philepittidaz, Acanthidosittidas, and Eurylm- 

 •midaz. 



^ The section which for want of a better name we have to call " Pseudosdnes " 

 has hitherto been found peculiar to Australia. 



