INTRODUCTION. 
153 
of geographic restriction. It is in the two typical 
genera that wo find tho most brilliant colours and 
changing tints, and those patches of playful colour 
on the throat and head which so particularly mark 
the Humming-birds. In these the principal colours 
are various shades of steel-blue, always with me- 
tallic lustre, the head and throat often with patches 
of green, blue, or violet, of a scale-like texture, and 
giving out fresh tints with every change of position ; 
but a marked difference in the rest of the arrange- 
ments is seen in the under parts being often of clear 
and very decided yellow, orange, or red, or being 
boldly marked with a broad bar of these colours. 
In these two genera, also, we see a slight develop- 
ment of the feathers springing from under the wings, 
which is often so beautifully displayed among the 
Humming-birds, and which also brings both, in 
part to resemble another suctorial family, — .the 
Meliphagidse or Honeysuckers. Here they are con- 
fined to small tufts of loose plumes, commonly of a 
yellow colour, but occasionally of a bright red : we 
have endeavoured to exhibit this structure in our 
Plates. It is in these forms also that we perceive 
the greatest variation in the form of the tail, which 
is in some long, at the same time having the plumes 
regularly graduating; in others tho two centre 
plumes only are much elongated, sometimes more 
than equalling the length of the bird, and in a few 
instances being slightly spatulate at the tips ; but 
in none of the known species have we an example 
of a forked tail. In the American portion of the 
