96 



BRITISH BIRDS. 



is confined to a very small space not extending anteriorly 

 beyond the level of the wrist- joint when the wing is 



fig. 1. 

 pterylosis of the black- throated diver (underside). 



The dotted areas represent the pterylaz or feather-tracts. 



closed, nor posteriorly beyond the level of the femur : 

 above it is bounded by the axilla, below by the flank- 

 feathers. The small dorsi-lateral space overlying the 



