414 Mr. A. R. Wallace on the Arrangement of the 



Picarise, wliicli is certainly wrong; while Sundevall unites 

 them in the same family with Rupicola, near to which genus 

 they must undoubtedly be placed in a natural arrangement. 



NoWj taking the four series of Passerine birds as here ar- 

 ranged, we find a marked and very curious distinction between 

 the American, and especially the typical Neotropical, fauna 

 and that of all the rest of the globe. Of the thirteen families 

 which are altogether confined to the New World, all but one 

 have the prevailing character that the first quill in the wing is 

 well developed in proportion to those which immediately suc- 

 ceed it ; and this is the case whether there are nine or ten 

 primaries in all. In the Old World, on the contrary, we find 

 the prevailing character of the wing to be, that the first quill 

 is either distinctly rudimentary, or very much reduced in size 

 proportionally to the succeeding quills ; so that out of twenty- 

 nine families which are especially characteristic of the Old 

 World, no less than twenty-two have this character. It is 

 further to be noted that the seven Old- World families which 

 have the first quill fully developed (including those with nine 

 as well as those with ten primaries) are all of them of com- 

 paratively small extent and little varied in structure. These 

 facts render it almost certain that the characters drawn from 

 the condition of the first two primai'ies, here made use of, are 

 really of great permanence, and therefore of high classificatory 

 value ; for if they had been less stable, and liable to frequent 

 change from family to family and from genus to genus, it is 

 contrary to all probability that they should present them- 

 selves with such an approach to uniformity in whole series 

 of allied families confined to the Old and the New Worlds 

 respectively. 



Another consideration in favour of the correctness of the 

 divisions here marked out is, that the best modern ornitho- 

 logists are nearly in agreement as to the mutual relations of 

 the families in Series A, C, and D respectively; but in the 

 attempt to intercalate the families of Series B among the 

 others, there has been as marked a diversity of opinion ; and 

 although the relations of several of these families to each other 

 have been admitted, no bond of union has been detected among 



