INTRODUCTION. 153 



of geographic restriction. It is in the two typical 

 genera that we find the 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 

 Meliphagidce 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 the 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 



