37° 
PIGEONS AND SAND-GROUSE. 
the first being the Columbince, in which the tail is never longer than the wings; 
this group containing the wood-pigeon, stock-dove, and rock-clove, from the last- 
named of which the domestic breeds of pigeon are derived. Of the first genus, 
Gymnophaps, only one species (G. albertisi ) peculiar to New Guinea is known, 
which is distinguished from the allied genera by having the legs feathered for two- 
thircls of their length, and a naked carmine space in front of and round the eyes. 
Rock-Dove and We next come to the large and universally distributed genus, 
Aiiies. Columba, containing about sixty species. All these birds resemble 
the two following genera in never having the legs feathered for more than half 
BOCK-DOVE nat. size). 
their length, while they differ in having the first flight-feather of the wing longer 
than the sixth. Space only permits of mentioning a few more important members, 
among which must be included the rock-dove or blue rock (C. livia), widely spread 
over Europe, and extending as far as India in the east, wdiere it meets the nearly 
allied but grey-rumped species (G. intermedia ); southwards it ranges to the north 
and west coasts of Africa, where another closely related form ( C. gymnocyclus ) is 
found, differing only in having the plumage dark bluish or blackish slate-colour, 
and perhaps descended from domestic pigeons. In the original wild stock of the 
blue rock, the plumage is grey, the rump white, and the neck and upper breast 
metallic green and purple, while there are two narrower black bars across the 
wing and a broader one across the end of the tail. It is found in a wild state 
where caves and deep fissures exist, and is common along the northern coasts of 
