530 Mr. G. L. Bates on the Reversed [Ibis, 



other feathers, consisting of the minor and the marginal 

 under coverts^ that are 7-eversed; but considered with refer- 

 ence to the position that* seems most natural for the under 

 surface of the wing, — the position of the majority of the 

 feathers, — the two rows, the major and the median under 

 coverts, are reversed : hence the term " reversed coverts " is 

 applied to them. The fact of the peculiar position of the 

 reversed coverts was pointed out by Sundevall (1), but his 

 explanation of it must give place to that of Wray (2), which 

 has since been generally accepted, and is here given in the 

 author's own words (p. 353) : — " These feathers or their 

 antetypes were originally on the dorsal surface and have 

 been carried down to the ventral in the formation of 

 the ' ala membrana * by the excessive development of the 

 remiges and tectrices majores.^^ Wray noted that the 

 embryo wing is rounded in section, there being no '^ ala 

 membrana," and that the inferior major and median coverts 

 are at first "distinctly more on the dorsal half of the 

 rounded edge of the wing than its ventral." 



When one becomes accustomed to thinking of the reversed 

 coverts as really belonging to the upper surface of the wing, 

 though pushed over to the under surface in the manner 

 described, other facts besides their reversed position come 

 to be understood. Sundevall (1) noted that " they often 

 retain rigidity and straightness and an external form which 

 give them some resemblance to quill feathers." It may be 

 added that they sometimes resemble even in colour the 

 remiges and upper coverts, and contrast with the minor 

 under coverts. The reversed under coverts in the large 

 Plantain-eater, Corythceola cristata, have their dorsal sur- 

 faces of the same beautiful blue colour as those of the 

 remiges, though these surfaces lie flat against the bases of 

 the remiges and upper coverts and are never exposed to the 

 light, while the exposed vential surfaces are dull black like 

 those of the remiges, and like other feathers of the under- 

 side of the wing : thus the reversed coverts are brightly 

 coloured exactly like the upper wing-feathers even though in 

 their case the bright colour is never seen, 



