2212 The Zoologist— July, 1870. 



"70; middle toe and claw 100; outer do. the same; inner do. 85; 

 bill — chord of culmen (including width of knob) '40 ; along rictus "60 ; 

 gonys '25 ; height at base '30 ; width at base slightly less. 



The preceding is a description of the perfect plumage of this 

 species, which is of comparatively infrequent occurrence. The usual 

 state of plumage of the bird as met with in colleclions is much as 

 follows : — Bill as described above ; filamentous feathers much as 

 above described, but rather shorter and more sparse, and scarcely 

 appearing behind the eye and along edge of side of lower javy. Upper 

 parts plumbeous-black, sometimes slightly interrupted in its con- 

 tinuity by a few whitish feathers about the scapulars; the primaries 

 grayish black, paler on their inner webs; secondaries grayish white 

 at their tips. Under parts white, as before, but very sparsely marbled 

 or waved with dusky ; least so on the abdomen, most so on the sides 

 and breast, where the blackish so increases in amount as to appear 

 more or less conlinuous with that of the upper parts. Chin and sides 

 of jaw as above described, but throat white, immaculate. The dusky 

 mottling varies greatly in amount and in intensity with different 

 specimens. Sometimes it is reduced to a k\v isolated touches here 

 and there, and again it is found to give the prevailing colour to the 

 under parts. That specimens in this mottled condition are not 

 immature, is proven by the fact that the bill is fully grown and 

 provided with a well-developed tubercle, and that the forehead is 

 thickly covered with white setaceous feathers. The mottling, how- 

 ever, is confined to the tips of the individual feathers, whose bases 

 are pure white; and is thus apparenilij of a temporary and transient 

 character, like that so frequently met with in young or winter 

 specimens of gulls and petrels. It may be a seasonal feature, or one 

 only found in birds of a certain age ; and yet numerous facts tend to 

 indicate it as a character of perfectly mature birds. Were one to 

 examine a specimen with the usual moderate amount of mottling on 

 the under parts, and notice the fact that the blackish occupies only 

 the tips of the feathers, he could not fail to be impressed with the 

 analogy just now hinted at, and to conclude that with advancing age 

 the mottling would grow less and less, and finally disappear, leaving 

 the under parts pure white, as in pusillus. Such, however, appears 

 not to be the case. Specimens whose age is attested by a fully 

 developed bill and well formed tubercle, are those most mottled below 

 with blackish. And yet, no specimens have been found with the 

 breast or any other part of the under parts uninterruptedly black, 



