170 ON THE CLASSIFICATION OF BIRDS. 
manner in which the primary groups pass into eacl 
other: such assertions, when not founded upon com 
plete analysis, can only be received as mere opinion 
we shall therefore merely offer a few remarks on th 
analogy of the pigeons to the Grallatores, in further 
proof of the station given to this family in our arrange. 
ment of the Rasores. 
(192.) On looking to the three aberrant groups of the 
Rasores, in reference to the primary orders of birds, — 
the ostriches (Struthionide) evidently represent the 
Natatores, by their broad, depressed, and somewhat duck— 
shaped bill—by their imperfect toes—by their great size— 
and, lastly, by the wings being as unserviceable for flight 
as are those of the penguin. Here, then, we have a 
certain point from whence to start ; and the question be- 
comes reduced to the narrower compass of which family, 
in short, represents the Grallatores and the Tenui- 
rostres. These groups, it will be remembered, are re- 
markable for their soft and slender bills ; so also are the 
pigeons: the nostrils are large, long, and covered by a 
thin soft membrane : the pigeons are the only Gallinacea 
which answer to this description; they have the most 
slender bills, and their nostrils are long, large, and soft. 
Grallatorial birds have great strength and power of wing: 
the humming-birds, —a grallatorial type, — fly swifter than 
swallows: and pigeons are the only rasorial birds which 
possess this power to any extent; for itis well known 
their flight, in general, is very rapid. The wading 
order is particularly remarkable for being destitute of 
crests,—one of the most distinguishing characters of 
the Scansores and the Rasores: so also are the pigeons — 
one species only out of near 150 being furnished with 
this appendage ; this being a rasorial type in its own 
circle. Finally, we have a singular analogy preserved 
between the cuckows and the pigeons, by the rump 
feathers being of that peculiar formation which belongs 
to the orioles, the caterpillar-catchers, and several — 
other tenuirostral types scattered among the perchers. 
With these strong relations before us, we feel no doubt — 
