244 NOTES ON SOME OF OUR INDIAN STONE CHATS. 



It is clear that with such an unbroken gradation in dimen- 

 sions, as I have above exhibited, no arbitrary line can be drawn, 

 and those on one side of this called one species, and those 

 on the other, another. 



I cannot doubt that my Sikhim and Syree birds fully re- 

 present Dr. Tristram's robusta, but after the most painfully 

 minute investigation of all those details, out of which specific 

 differences may often be established, I am utterly unable to 

 discover any one poiut, however minute, except that of size 

 whereby these two specimens may be divided from the rest. 



Now it is impossible to draw the line at 3"0, and say these 

 are robusta, but the precisely similar 2*95 wing birds are indica, 

 or at 2*95 and reject the 2'92, or at 2'92 and reject the 29, &c. 



All that Ave can say is, that almost all the largest birds exhi- 

 bit the type of coloration, indicated by Dr. Tristram as the 

 characteristic of his robusta ; that as the birds decrease in size, 

 this type of coloration grows less and less frequent ; and that 

 all the very largest birds are from Assam, the Eastern and 

 Central Himalayas ; but it is impossible, in the face of the 

 facts above set forth, to establish a species on grounds like these, 

 and my conclusion is that, if I have rightly identified P. robusta 

 (and this seems scarely doubtful), the form indicated by this 

 name is not entitled to specific separation. 



If Dr. Tristram can point out any clear and specific diagnosis, 

 well and good ; I shall be delighted to test this in my tolerably 

 large series, but if he has already said, all he can in regard 

 to this supposed species, it must I conceive be suppressed. 



When 1 suggested that macrorhyncha might be identical 

 with robusta, I had not made out what the latter was. Now 

 that I have done so, I find that what I identify as robusta has 

 a bill precisely like that of indica, larger of course than the 

 bills of small specimens, but of precisely the same shape. 

 Macrorhyncha, on the other hand, has a much slenderer bill, very 

 like that of rubetraoides and quite unlike that of indica. 



Moreover, the birds I identify as robusta exhibit the pure 

 white tertiary greater coverts or under scapulars (I am in 

 doubt which to call them) which characterise rubicola, rubetra, 

 indica and rubetraoides, whereas these are entirely wanting in 

 the two female macrorhynchas I possess. 



I therefore entertain no doubt now that macrorhyncha is a 

 good and distinct species. 



Pratincola Hemprichii is characterized by a good deal of 

 white, very variable however in extent, at the base of the tail. 

 I examined the whole of the 125 specimens above referred to, 

 to see if by chauce there was any Hemprichii amongst them, 

 but found no trace of white on the tails of any one of them. 



