138 PROCEEDINGS OF THE ACADEMY OF. 



Description. Form: The bill, measured from the frontal feathers, is about 

 three- fourths as long as the skull, rather more than two-thirds the tarsus. Its 

 height at the base is just about equal to the width. Its height at the point of 

 greatest convexity of the unguis hardly exceeds that at the middle of the culmen. 

 The unguis is not very strong, its convexity only moderate. The commissure 

 at first curves gently upwards, then still more gradually downwards for the 

 whole length of the bill, and then is pretty strongly deflected along the edge 

 of the unguis. The outline of the lower mandible is about straight to the 

 unguis, a little concave thence to the tip. The length of the nasal tubes is 

 a little less than a fourth that of the culmen. The outline of the feathers on 

 the upper mandible is the segment of a perfect circle. The folded wings just 

 about reach to the end of the tail. The second primary is nearly as long as 

 the first, the rest successively more and more rapidly graduated. The tail is 

 contained about two and a third times in the wing from the carpal joint. It is 

 much rounded, the lateral rectrices all regularly graduated; the exterior just 

 three-fourths of an inch shorter than the central pair. The tarsus is just as 

 long as the middle toe without its claw. The external toe and claw is a little 

 longer than the middle toe and claw. The tip of the inner claw falls short of 

 the base of the middle one. The claws are all nearly or quite as broad as 

 high, being much dilated on their inner edges. 



Color : The entire upper parts are of a deep lustrous black, with a soup- 

 con of brownish, especially when the feathers are old and worn. On the 

 front and sides of the head and neck the black has a grayish or plumbeous 

 cast. This color extends on the sides of the head much below the eyes, in 

 fact quite to the throat, but it is more or less marbled with white. The 

 under eyelid is pure white, in marked contrast with the surrounding black. 

 On the sides of the neck the white extends further round towards the nape ; 

 on the sides of the breast, on the contrary, the color of the back extends a 

 considerable distance, it being of a decided greyish plumbeous hue, and gra- 

 dually becoming more and more marbled with white till it entirely disappears. 

 The primary quills are black, as are their shafts, their inner webs fading 

 into dull grayish brown. The entire under parts, from chin to under tail 

 coverts, are pure white, with the single exception of a few feathers just on the 

 Hanks, and of the outer webs of the exterior row of under tail coverts, which 

 are plumbeous black. The under surfaces of the wings and the axillary 

 feathers are pure white, with a slight marbling of blackish just along the 

 bend of the wing. The caudal rectrices are like the primary quills ; the in- 

 ferior surfaces of their shafts grayish white. Bill deep greenish black, some 

 part of the lower mandible yellowish. Part of outer side of tarsus, whole of 

 outer side of exterior toe and the claws brownish black ; rest of feet light 

 yellowish, including the webs. 



Average dimensions : Bill along culmen 1.40; height at base .45 ; width 

 about the same ; along rictus 2.10 ; from feathers on side of lower mandible 

 to its tip 1.40 ; wing from the carpal joint 9 25 ; tail : exterior feathers 3.25, 

 middle 4.00; amount of graduation .75; tarsus 1.80; middle toe and claw 

 1.90; outer do. 2.00 ; inner do. 1.55. Total length about 14.00; extent of 

 wings about 33.00 



Variations. As to dimensions, these are quite considerable. As usual 

 among Puffini, the bill differs a good deal in absolute size, as well as in 

 robustness, generally preserving its shape, however, quite contantly. The 

 longest bill before me measured 1.50 ; the shortest 1.30, along culmen, with 

 a corresponding difference in other dimensions. The wing from the carpal 

 joint varies nearly half an inch, and the tail to a corresponding degree. The 

 total length of tarsus and toes varies about a third of an inch. In color the 

 species is more constant, the chief variation being in the greater intensity or 

 more decided brownish tint of the black of the upper parts. Younger speci- 

 mens have more marbling of the plumbeous black and white on the sides of 

 the breast, the color sometimes reaching nearly or quite across the breast, or 



[April, 



