COLUMB^ 305 



COLUMBiE ' 



Defimtion. — Aftershaft absent. Oil gland absent or nude. Crop 

 present. Ceeoa nipples. Syrinx with, asymmetrical extrinsic 

 muscles. Of the leg muscles ABX al-ways present ; deep plantar 

 tendons of type I. Biceps slip present and peculiar in form. 

 Skull schizognathous, sohizorhinal. Basipterygoid processes 

 present, except in Didus. 



This group of birds contains something like 458 species, 

 which are divided into sixty-eight genera. Pigeons are cos- 

 mopolitan in range, and show a considerable amount of 

 structural variation. 



The absence of an aftershaft and the often rudimentary 

 condition of the oil gland are among the most important 

 variable external characteristics of the pigeons. The latter 

 is never feathered, and is sometimes totally absent. But its 

 presence or absence cannot be made use of as a fact of great 

 systematic importance ; for we find in the same genus 

 Ptilopus two species, Pt. coronulatus and Pt. superbus, with 

 a minute oil gland, and two others, Pt. assimilis and Pt. 

 puella, from which the gland has entirely disappeared. 



The rectrices vary in number frpm 12 (e.g. Golumhula) 

 through 14 (e.g. Phaps), 16 (Goura), to 20 {Otidiphaps) . 

 But the variations do not invariably coincide with the limits 

 of genera. Phaps ehalcoptera has 16 rectrices, P. elegans 

 only 14. Phlogoenas Stairi has 12 rectrices, P. cruentata 14. 

 There are other examples. Though for the most part 

 aquincubital, it is remarkable to find in Golumhula a quinto- 

 cubital bird (Mitchell) . 



I have by me a careful manuscript account of thepterylosis 

 of Didunculus by Mr. Forbes. The dorsal tract is strong 

 and broad upon the neck, narrowing a little below ; where 

 it narrows it becomes stronger. Below the shoulder it bifur- 

 cates and becomes suddenly weak ; below this point the whole 

 dorsal region is covered with a weak and diffused feathering, 

 which is especially weak over the head of the femur. In the 



' C. J. Temminck, Sistoire Natii/relle Oinirale des Pigeons et des Gallinacies. 

 Amsterdam et Paris, 1813-1815. 



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