278 Prof. R. Collett on the Occurrence 



fore, before their full development, have bills of about the 

 same colour. As a rule, however, the bill is alvvays of a 

 lighter tinge in C. adamsi, and its shape, even at a very early 

 stage (together with character No. 5), furnishes a recognizable 

 difference. 



(4) The Colour of the Lower Back. 



In all old birds of C. adamsi the lower part of the back is 

 unspotted, whilst in C glacialis that part has small white 

 spots like the upper part of the rump. There, however, 

 appear exceptionally on this part of C. adamsi a spot or two, 

 and these spots may be quite evanescent in C. glacialis. 



(5) The Colour of the Shafts of the Wing -feathers. 



This is a character of special value in C. adamsi, being the 

 only distinguishing feature present even in the young bird, 

 and its investigation will determine in an instant to which 

 species any individual specimen is to be referred. In all the 

 individuals of C. adamsi which I have hitherto examined, 

 the shafts are light horn-brown, except the tips, which are 

 brownish black. In this character there is no difference be- 

 tween young and old birds. In C. glacialis the whole outer 

 half of the shafts of the wing-feathers is brownish black. 

 The tendency in C. adamsi to have the horny portions of the 

 body more lightly coloured than in C. glacialis is, but to a 

 less degree, visible in the shafts of the back-feathers and 

 possibly also in the living individual as regards the colour of 

 the claws. 



(6) The Lower Neck-bar. 



The lower neck-bar of C. adamsi affords several cha- 

 racteristics. The white stripes are broad ; their number 

 seldom exceeds ten, whilst in C. glacialis there are double 

 that number or more. The throat-bar also has always a few 

 stripes less than in C. glacialis. The neck-bar is compara- 

 tively narrow, and its width would be contained twice (or 

 more) in the width of the broad black collar beneath. In 

 C. glacialis both bars are about equal in width ; occasionally 



