414 Mr. A. R. Wallace on the Arrangement of the 
Picariss, which is certainly wrong; while Snndevall unites 
them in the same family with Rupicola, near to which genus 
they must undoubtedly be placed in a natural arrangement. 
Now, 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 primaries, 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 
