CHAP. XVIII.] BIRDS. 301 



3, the Oriental 1, the Ethiopian 1, and the other regions have 

 no peculiar families. 



The distribution of the Passeres may be advantageously 

 considered as divided into the five series of Turdoid, Tanagroid, 

 Sturnoid, Formicarioid, and Anomalous Passeres. The Turdoid 

 Passeres, consisting of the first 23 families, are especially 

 characteristic of the Old World, none being found exclusively 

 in America, and only two or three being at all abundant there. 

 The Tanagroid Passeres (Families 24-33) are very characteristic 

 of the New World, five being confined to it, and three others 

 being quite as abundant there as in the Old World ; while there 

 is not a single exclusively Old World family in the series, 

 except the Drepanididse confined to the Sandwich Islands. 

 The Sturnoid Passeres (Families 34-38) are all exclusively Old 

 World, except that two larks inhabit parts of North America, 

 and a few pipits South America. The Formicarioid Passeres 

 (Families 39-48) are strikingly characteristic of the New World, 

 to which seven of the families exclusively belong; the two 

 Old World groups being small, and with a very restricted 

 distribution. The Anomalous Passeres (Families 49-50) are 

 confined to Australia. 



The most remarkable feature in the geographical distribution 

 of the Passeres is the richness of the American continent, and 

 the large development of characteristic types that occurs there. 

 The fact that America possesses 14 altogether peculiar famili^5s, 

 while no less than 23 Old- World families are entirely absent from 

 it, plainly indicates, that, if this division does not represent the 

 most ancient and radical separation of the land surface of the 

 globe, it must still be one of very great antiquity, and have 

 modified in a very marked way the distribution of all livinp- 

 things. Not less remarkable is the richness in specific forms 

 of the 13 peculiar American families. These contain no less 

 than 1,570 species, leaving only about 500 American species in 

 the 13 other Passerine families represented in the New World. 

 If we make a deduction for those Nearctic species which occur 

 only north of Panama, we may estimate the truly Neotropical 

 species of Passerine birds at 1,900, which is almost exactly 



