191B.J On the Structure of the Feather. 243 



p. 329. For Monticola cyanus read 



Monticola solitarius. 



Tardus solitarius Linnseus, Syst. Nat. 1758, p. 170 : 

 Italy (ex Willugliby). 



The oldest uame of the Blue Rock-Thrush is that of the 

 lOtli ed. of Linnaeus Syst. Nat. ; in the 12th ed. it was 

 re- named Turdus cyanus. 



p. 351. For P or pJiyrio porphyria read 



Porphyrio madagascarieusis. 



Gallinula madayascariensis Latham, Index Orn. SuppL 

 1801, p. Ixviii : Madagascar. 



Dr. Hartert (Nov. Zool, xxiv. 1917, p. 265) has recently 

 shown that there is no justification for using the natne 

 Porphyrio porphyrio (Linn.) for this African species, and 

 that the first available name for it is that of Latham. 



XIII. — A Note on the Structure of the Feather. 

 By John S. Gladstone, F.Z.S.. 



(Plates V-VII.) 



For some time past 1 have been engaged on the photographic 

 analysis of a feather, and my attention has been concentrated 

 on the glazed portion of the underside of the primaries of 

 certain birds. Chandler (University of California Publi- 

 cations, Zoology, xiii. 1916, pp. 243-446), referring to the 

 subject states : — 



" The ventral edges of the rami are produced into 

 horny keels usually with no evident cell structure, 

 known as the ventral ridges. Although in the great 

 majority of birds the ridge forms only a narrow, incon- 

 spicuous border for the ramus, in a few birds it is 

 extraordinarily developed as a very thin translucent 

 film, which bends distally and overlaps the following 



