NATURAL SCIENCES OF PHILADELPHIA. 77 



tlie whole length of the sides under the wings streaked with dusky or slatj-- 

 brown. Bill black ; mouth yellow; iris brown ; legs and feet blackish. 



Adult, winter plumage. — As before; the rich brown of the head darker in hue, 

 arid more like the rest of the upper parts ; the white of the under parts extend- 

 ing to the bill, upon the sides of the head to or slightly aliove the level of the 

 commissure, upon the side of the neck so far around as to leave only a narrow 

 isthmus of dark color, which is somewhat interrupted by white mottling. The 

 white shades gradually into the darker color, without a trenchant line of de- 

 marcation, and varies greatly in its precise outliue. Usually a pretty well de- 

 fined spur of dark color runs out backwards from the eye into the white of the 

 sides of the occiput, the spur occupying the borders of the postocular furrow 

 in the plumage. On the sides of the lower neck, just in advance of the wings, 

 the dark color extends in a point further than it does higher up, showing the 

 extent of the dark brown of the summer vesture. 



Young, of the first winter, are colored precisely like the adults, but may be 

 always distinguished by their much shorter and slenderer bills, which are in 

 great part light colored (yellowish). The feet are also much tinged anteriorlv 

 with yellowish. 



Fledgelings are brownish-dusky, the breast and abdomen white ; and with a 

 few dull whitish streaks upon the head and hind neck. 



Dimensions. — Adult. — Length about 17-00 ; extent 30-00 ; wing 8-00 ; tail 

 2-25 , tarsus 1 --lO ; middle toe and claw 2-10 ; inner do. 1-70; outer do. 2-00 : 

 bill along culmen 1-75, along rictus 2-50 ; along gonys 1-15; depth at base 

 •55 ; width at same point .30. Bill of young, first winter : culmen 1-50 ; rictus 

 2-2.') ; gonys -90 ; depth at base -45 ; width at base -25. 



This species is well known to vary to a certain degree in size, and in the 

 precise shape of the bill. The dimensions above given represent very nearly 

 the average of a large suite of specimens measured. In colors, the variations, 

 though considerable, are unimportant, consisting in the difference in shade of 

 the colors of the upper parts, and the difference in precise outline of the dark 

 and light colors about the head and neck, in summer as well as in winter spe- 

 cimens. Specimens just before the renewal of the feathers have the upper 

 parts distinctly barred or waved with gray, owing to the fading of the tips of 

 the old feathers ; and the wing and tail feathers light dull gray. The difference 

 in intensity of coloration depends chiefly upon season, though individual pe- 

 culiarities may be observed. Very highly plumaged birds have the upper parts 

 almost uniform in hue. 



The synonymy of this species is very extensive, and somewhat intricate, 

 though it is possible to collate it with much accuracy and certaint}-, provided 

 more labor be bestowed than the importance of the matter warrants, as seems 

 to the writer to have been the case in the present instance. In consequence of 

 the peculiarly obvious nature of the characters which distinguish the several 

 closely allied species from the present one, even the brief diagnoses of the 

 most antiquated authors may be recognized and identified, in the majoritv of 

 instances. But it is curious to uote that the various names most in voo'ue for 

 two or three species of this genus have been so frequently interchanged, and so 

 variousl}- applied, not only in a specific, but in a generic, sense, that they have 

 really come at last to mean nothing more than simply Murre or Guillemot. It 

 is absolutely necessary to refer to a writer's description, or his authorities 

 quoted, before we can have any idea to what species he alludes under any given 

 name; — certainly a very discouraging state of affairs, and one not placini^- orni- 

 thologj' in a very creditable light. 



The present species is Linnaeus' troille, of Fn. Suec. 1761, and S. X. 1766, 

 and is so regarded by most writers. It is the lomvia of Briinnich, which name 

 is usually adopted by those writers who date Linn^us' prerogative of prioritj' at 

 1766. It is minor of Gmelin, who to a description of this species adds the 

 synonyms of two others. It is not troille of Briinnich, nor lomvia of Linnaeus. 



1868.] 



