PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 213^ 



found in the black cross-bar of the wing-speculnra, a peculiarity to be 

 discussed more iu detail further ou, when speaking of C. (jrylle. 



Finally a character should be mentioned which may seem trifling, 

 but nevertheless is very constant. In (jrylle and mandtii the black 

 has a faint but decided greenish gloss, which in colmnha is substituted 

 by a less glossy slate-colored wash on the back, with indication of pur- 

 plish on the abdomen. In old museum specimens of colamba the tinge 

 is rather brownish, but the absence of green is always well marked. 



Xo one who ever had the opportunity of comparing authentic speci- 

 mens of C. colitmha can doubt its absolute validity as a species. 



It has already been pointed out by Prof. A. ^S^ewton, aud I am in the 

 position of being able to indorse his statement most em])hatically, that 

 "tbere exists an unfailing means of differentiating Ccpphns mandtii from 

 C. (jryUe. This lies in the feathers which form the conspicuous wing- 

 S])ot. In the more northern form from Greenland and Spitsbergen 

 they are pure white at the base, even in immature birds, while iu the 

 true C. {/rijUe, from our own islands, Iceland and ^STorway, with its 

 stouter bill, these feathers are always black at the base, forming an en- 

 tirely, or almost entirely, concealed baud across the wing-spot." It 

 may be added, however, in order to avoid mistakes, that not all "the 

 feathers which form the wing-spot" are meant, but only the large cov- 

 erts of the secondaries, the so-called "greater upper wing-coverts." 



rig. 1. Cepphvs cohivihu, ad. Fig. 2. Cepphus grylle, SlA. Tig. 3. Cepphus mandtii, &A.. 



The large series before me is easily divided into two groups. In the 

 one the greater wing-coverts are wLite to tiie very base, with or with- 

 out an indistinct dusky line along the basal half of the shaft (fig. 3); all 

 birds thus colored have a slenderer bill. In the other group the greater 

 wingcoverts are black or blackish for about their basal half or more, 

 with a sharp outline towards the white of the terminal half (fig. 2); all 

 birds thus marked have the bill stout and strong. The former belong- 

 to C. mandtii j)roper, the latter to the true C. (jrylle. The black bases 

 of the greater wing-coverts in (jrylle form a continuous black cross-bar 



