415 
Families constituting the Order Passeres. 
the whole series. This bond of union, I maintain, is found 
in the total abortion of the first primary quill; and although 
in the case of some of the families we may not see any other 
character to unite them, this should not militate against giving 
due weight to a structural peculiarity which is found to be 
absolutely constant throughout all the species of several ex¬ 
tensive families, and to confirm, in many cases, the conclu¬ 
sions which ornithologists have arrived at from other cha¬ 
racters. It is therefore the separation of the families con¬ 
stituting the “ Tanagroid Passeres ” as a distinct group which 
forms the main feature of my proposed arrangement, and in 
which its chief value (if any) is to be found. 
As it is not always possible to determine the number of the 
primary quills without" injuring the specimen, and not pos¬ 
sessing duplicates of many of the requisite forms, I have in 
general taken the statements of Professor Sundevall to be cor¬ 
rect. He has devoted himself for many years to the special 
study of the details of external form and structure in birds, 
and in the work already quoted has, in most cases, given the 
number of the primaries and the nature of the first quill. 
But (as I think, very unfortunately) he has only occasionally 
given weight to this character in his classification, which de¬ 
pends mainly on the varieties of scutellation of the tarsi. 
This latter character can hardly have the high value he gives 
it, since it leads to such unnatural combinations as Larks 
and Hoopoes, Todus and Pipra , Irrisor and Epimachus— 
errors due in great part to his refusal to give any weight to 
purely anatomical characters. Yet in many respects his clas¬ 
sification is a great advance on most of those which have 
preceded it, since it defines every group by clear external cha¬ 
racters, which, if not always of the value he assigns to them, 
will be of great service to future workers at the classification 
of birds. 
The foregoing systematic sketch has been arrived at after 
often renewed attempts at a natural arrangement of Passeres, 
for the purposes of a work, on the Geographical Distribution 
of Animals, on which I have been some time engaged. The 
conclusions now set forth seem to me more satisfactory than 
