

122 Clark, Tail-feathers and Coverts. LApril 



order, and of these only two genera. In Selenidera, we find what 

 is probably the typical arrangement, 5-5, the inner coverts alter- 

 nating with the rectrices but the outer ones lying over them. The 

 extraordinary condition found in Ramphastos cuvieri is described 

 above (p. 117). 



Piciformes. The normal formula for woodpeckers seems to be 

 6-6, but the sixth covert is small and may be wanting, giving the 

 passerine formula, 6-5. Owing to a line of contour feathers extend- 

 ing down on each side of the pygidium and joining the series of 

 major coverts it is difficult to determine beyond question where 

 the coverts end. In the larger woodpeckers, particularly in 

 Phloeotomus, the middle rectrices are so stout the major coverts 

 seem to have been pushed further to the side than usual, so that 

 covert 1 lies between rectrices 2 and 3, covert 2 is between 3 and 4, 

 3 is over rectrix 4, 4 is over 5 and 5 and 6 are over 6. The genera 

 examined are Colaptes, Melanerpes, Den&rocopus, Picoides and 

 Phlwotomus. 



Passeriformes. All the specimens of passeriform birds exam- 

 ined showed the characteristic 6-5 arrangement, the middle pair 

 of rectrices apparently lacking coverts. Study of developmental 

 material alone can decide whether covert 1 is really wanting or is 

 merely displaced, though it seems probable that the latter is the 

 case. The genera examined, selected quite at random, are Tityra, 

 Xanthoura, Turdus, Trochalopteron, Acanthorhy?ichus, Petrochelidon, 

 Rombycilla, Piranga and Hedymeles. 



The question as to the significance of the data given above is 

 interesting but deductions must be drawn with care from such 

 fragmentary material. The subject is just opened up in this paper 

 and much more work must be done before the importance to be 

 attached to the condition of the major coverts can be determined. 

 It is possible that habits may play an important part in the arrange- 

 ment of the coverts in some cases. The recent interesting discov- 

 eries of Mr. C. W. Beebe regarding the nestlings of toucans and the 

 way they hold their tail suggests that the extraordinary arrange- 

 ment of the major coverts in Raviphastos cuvieri is the possible 

 result of such a habit. Whether there is any phylogenetic signi- 

 ficance in the number and character of the major, upper coverts 

 remains to be discovered but it is at least suggestive that the 



