that connect the Orders and Families of Birds. 421 
that the tribes which meet our earliest attention are those respect- 
ing which our information is most deficient; and where, conse- 
quently, we must feel most hesitation in deciding on the affinities 
which connect them, and the subdivisions into which they branch 
out. I shall not therefore at present dwell at much length upon 
this order, but shall content myself with a few brief observations, 
more particularly on such of the groups as containing European 
species, and being of course more open to examination, may be 
spoken of with some degree of confidence. 
There are three important groups in this order, which form 
distinct and prominent subdivisions of it; the families of Vultu- 
ride, Falconide, and Strigide, corresponding with the Linnean 
genera Vultur, Falco, and Strix. To these may perhaps be added 
a fourth group, the Gypogeranus of M. Illiger, which, though it 
has sometimes been disposed in a different order, is now, I believe, 
generally admitted to be a Bird of Prey. In this arrangement 
I feel every disposition to acquiesce. ‘The essential characters 
observable in the structure of the Gypogeranus accord accurately 
with those of the Raptores; and it bears a resemblance to the 
Grallatores, among which it is sometimes arranged, only in the 
length of its tarsi. But in judging by such insulated. characters, 
however striking or important, as only indicate a similarity be- 
tween groups not otherwise connected together by equally essen- 
tial particulars, it becomes necessary to consider whether the 
conformity of these characters may not be the result of a con- 
formity in habit or situation, which may incidentally assimilate 
the groups in which they are found, rather than of a natural affi- 
nity that determinately unites them. In other words, we ought 
to reflect whether an analogous mode of life or an analogous 
place of resort may not give rise to a partially analogous confor- 
mation. In the present case, the sandy and unsubstantial nature 
of the plains which these birds frequent, appears to me to demand 
312 a cor- 
