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the absence of any inflexion in the keel, the greater depth and the 

 apparent shortness of the rami give, as it were, a recurved appearance 

 to the bill that is quite characteristic. K the specimens are, as they 

 seem to be, in spring plumage, their much lighter color would enable 

 us to distinguish them at a glance from specimens of troille in corre- 

 sponding plumage, but not from specimens which, later in the year, 

 had become faded ; as well as can be ascertained from the dried skins, 

 the color of the bill and feet is the same in both birds. In the above 

 descriptions, I have given no measurements, as the differences between 

 the different species are so slight that I thought it preferable to pre- 

 sent them in a tabular form, so that they could be more easily com- 

 pared. In order to illustrate more clearly the difference in form of 

 the bills of the different species, I have had drawings * made of the 

 vertical and lateral profiles of the adults of the four species or 

 varieties, and also of the young of Briinnich's Guillemot, the first 

 winter, and of a nestling of the Californian variety. Of the four 

 species two can be readily distinguished. Briinnich's Guillemot by 

 the short, stout bill, and its white edge next the rictus which can be 

 seen at quite a distance, and the Bridled Gillemot by the white line 

 surrounding the edge and running down the feather furrow. The 

 other two do not present such striking differences, but I have found 

 no difficulty in distinguishing the specimens I have examined. 



* In selecting specimens for the drawings, I carefully avoided those that were 

 most marked, not wishing to give an erroneous impression. The specimen from 

 California has the bill longer than some of the others, but not so straight, and the 

 keel resembling more nearly than those of the others, that of ti^oille ,• in the draw- 

 ing it appears slightly intiexed, but this is not correct, in the bird it is perfectly 

 straight. The. line of the cutting edges of the upper mandible is much too straight 

 in the drawings of troille and ringi-ia ; this was occasioned by the distortion of the 

 part in drying, which I unfortunately forgot to caution the engraver about. 



