418 Clark, Pterylosis of the Wild Pigeon. [oct. 



separate. At the posterior margin of the sternum, there is a 

 distinct notch on the inner side of each ventral tract, which seems 

 to indicate the end of the sternal tract, widest just above the notch. 

 It is not certain that this notch is not an artefact but I believe it 

 would be at least indicated in the living bird. The ventral tracts 

 end at the anus but scarcely surround it. There is no connection 

 between the lower cervical or sternal tracts and the anterior end 

 of the humerals. 



The pterylosis of the adult Wild Pigeon has been determined by 

 the study of two excellent alcoholic specimens. Certain features 

 not clearly shown by one are easily distinguished on the other. 

 The striking feature of the pterylosis is the extent to which the 

 tracts cover the bird; the increase in their width during growth 

 from nestling to adult is really extraordinary. Looking at the 

 dorsal surface of the plucked bird the first impression is that there 

 are no apteria but a closer inspection reveals a few small areas free 

 from contour feathers and brings out the fact that the contour 

 feathers are thickly placed on the main tracts and more sparsely 

 distributed on the intervening spaces. The whole upper surface 

 and sides of head and neck are quite uniformly feathered, some- 

 what sparsely on the occiput but quite densely on the neck. The 

 fork of the upper cervical tract can be distinguished by its thicker 

 feathering but there is no apterium between its halves or between 

 it and the dorsal tract. There are no apteria either between the 

 dorsal tract and the humerals but the intervening skin is uni- 

 formly, though not thickly, covered by contour feathers. The 

 humeral tracts are wide and thickly feathered; just outside them 

 there is, on each wing, an apterium about 25 mm. long by 8 mm. 

 wide, running nearly parallel with the humerus. The mid-dorsal 

 apterium is about 60 mm. long, 4 mm. wide at middle and tapering 

 to each end. It is therefore relatively larger than in Nitzsch's 

 figure of Columba, but it is greatly reduced (relatively of course) 

 from the condition shown in the young Ectopistes. At the upper 

 end of each femur there is a small apterium about 10 mm. in vertical 

 length by 7 mm. in width. At the side of the pygidium, at the 

 base of the outer rectrices is a still smaller space not quite 6 mm. 

 square. All the rest of the dorsal surface is covered by the contour 

 feathers of the dorsal and femoral tracts. The outer posterior 



