470 



On the Tail-feathers of the Dabchick. 



some of the apparent coverts are not in reality degenerate 

 rectrices ; but on the whole it does not appear that more than 

 eight can be regarded as answering to rectrices. These, 

 with their coverts, are arranged in a double series, one on 

 either side of the middle line and running parallel with one 

 another, leaving a well-marked apterion between them. 

 The slight concavity which these two rows enclosed in the 

 specimen originally examined — which caused me to describe 

 them as arranged in the form of a horseshoe — was, 

 I find, an individual peculiarity. As a matter of fact, the 

 two rows — eliminating the coverts — run parallel one to the 



Text-fig. 10. 



„-^ 



Tail-feathers of Podicipes fluviatilis. 



Section through the tail, exposing the caudal vertebrae, to shew the 

 relation of the rectrices to the pygostyle. 

 B. Superficial appearance of the bases of the rectrices. 



C.V. = Caudal vertebrae. P. = Pygostyle, 



0. = Oil-gland. R. = Rectrices. 



other, and, be it noted, have their ventral aspects turned 

 towards each other, as in many Gallinaceous birds. 



This peculiar arrangement would seem to have come about 

 as a consequence of the degeneration of the caudal vertebrae, 

 and the shortening of this region of the vertebral column 

 attendant thereon : the rectrices having been thus slowly 



