578 Letters, Extracts, Notices, ^c. 



1 



Heligoland, 



August 26, 1&89. 



Sir, — Whilst subjecting my manuscript on the Ornis of 

 Heligoland to a final revision, it appeared to me that there 

 exists as marked a specific difflerence between specimens of 

 Phylloscopus proregulus from Siberia and those from India, 

 as there is between Ph. super ciliosus and Ph. humei. In both 

 instances the Siberian bird differs from that of India in 

 general colour of plumage, which in the former is sufi"used 

 with a bright lemon-yellow, approaching and partly sur- 

 passing that of P. sibilatrix, whereas the colour of the latter 

 consists entirely of a dull brownish olive-yellow, verging in 

 P. humei, in many instances, towards ashy grey. But 

 although the difference in coloration of a series of skins 

 from Siberia and a series from India when placed alongside 

 each other is a very prominent one, still the specific distinction 

 becomes much more convincing when the wing-formula of 

 these birds is subjected to a comparative examination. 



In the Siberian bird the 2nd quill is of equal length with 

 the 8th, in the Indian bird wdth the 10th; in the former 

 bird the 2nd quill is only 6 millim. shorter than the point of 

 the closed wing, in the latter this difference amounts to 

 10 millim. ; and whilst in the Indian bird the 2nd quill is of 

 equal length with the longest of the three posterior quills, it 

 is in the Siberian from 6 to 7 millim. longer. 



Further, in the Siberian bird the 3rd, 4th, and 5th quills 

 are of equal length and form the point of the closed wing, 

 whereas in the Indian one such is the case with the 4th, 5th, 

 and 6th quills, the 3rd being 3 millim. shorter than these. 



These measurements are derived from eight skins, four of 

 them being of Siberian origin and four collected in India. 

 The proportions of the quills in each of these series being 

 so constant — diff'ering perhaps from one half to one mil- 

 limetre — and the colour of them being likewise distinct, 

 there seems to be no reason for doubt that the Indian bird 

 has as well-founded a claim to specific separation from the 

 Siberian Phylloscopus proregulus as P. humei has from 

 P. super ciliosus, P. tristis from P. fuscatus, or P. trochilus 



