NATURAL SCIENCES OF PHILADELPHIA. 143 



177. New Holland to Cape Horn. Gould, Am. et Mag. Nat. Hist. xiii. 

 1844, p. 363. From Cape of Good Hope to Van Diemen's Land. 

 sBstrelata leucocephala, Bonap. C. A., 1856, ii. p. 189. 

 ? Procellaria alba, Grnelin, S. N. i. pars ii. 1788, p. 565. Vieill. Nouv. Diet. 



1817, xxvii. p. 420. 

 ? Daption album, Shaw, Oen. Zool., 1825, xiii. p. 246. 

 ? Procellaria variegata, Bonnrerte, fide Bp. 

 Procellaria vagabunda, Solander, Mss. fide Bp. 



Habitat. South Pacific and Indian Oceans. 



Form.* Bill much shorter than the skull, but slightly less than the tarsus, 

 about two-thirds the middle toe and claw ; very robust, as broad as high at 

 the base, compressed in the rest of its extent. Unguis of upper mandible 

 very large, strong, deep, convex, much decurved, the tip acute ; the elevation 

 of the unguis beginning so near the nasal tubes as to leave but a short and 

 very concave extent of culmen proper. Lateral lamina? large, strong, wide, 

 inflated, deep at the base ; superior margin nearly straight, running obliquely 

 downwards and forwards from the frontal feathers to the commissural edge of 

 the unguis ; its lower margin sharp, a little inflected, very convex in outline. 

 The commissure is not very sinuate from the angle of the gape to the unguis. 

 The under mandible has a very distinct and deep lateral sulcus, which is 

 widened at both ends. The inferior unguis is large and strong, its tip much 

 decurved and acute, its gonys very concave, its angle at the symphysis pro- 

 minent but not acute. The outline of the inferior mandibular rami is a little 

 concave ; the interramal space is feathered nearly to the symphysis. The 

 nasal tubes are short, broad, somewhat depressed, their outline nearly 

 straight and ascending a little from base to apex ; the latter obliquely trun- 

 cated and emar^inated. The frontal feathers overlap the culmen, nearly in a 

 straight line or with a slightly convex outline ; thence immediately retreating 

 gradually backwards as they descend the sides of the bill. Those on the 

 lower mandible do not extend further than a point perpendicularly below 

 those on the culmen. 



The wing is of the ordinary length and shape. The tail is comparatively a 

 little shorter and less graduated than in hasitata, and is contained a little 

 more than twice in the wing from the carpal joint. 



The tibia? are feathered to within half an inch of the joint. The tarsi are 

 short, about three-fifths the middle toe and claw, moderately stout, but little 

 compres-ed, with the usual small subhexagonal reticulations. The tip of the 

 inner claw just reaches the base of the middle one. Uuter toe longer than 

 the middle ; but the tip of its claw does not quite reach to the tip of the 

 middle one. Claws all long slender, little curved, acute, compressed, the 

 middle one somewhat dilated on its inner edge. Hallux short, slender, 

 straight, acute, conical, sessile. 



Color. Bill pure intense black. Tarsi, and basal half or more of the toes 

 and webs flesh -colored ; yellowish when dried. Rest of toes and webs, in- 

 cluding the whole aspect of the outer toe, blackish. 



The head all around and the whole under parts are pure white. But a well- 

 defined bar of slaty or cinereous black passes through the eye. The upper 

 tail coverts and superior surface of the tail are clouded with light grayish 

 rinereous. On the nape the white of the head begins to be shaded with 

 pearly gray which deepens as it descends adown the back of the neck on the 

 interscapulars and dorsal parts generally into grayish slate ; which a^ain 

 lightens on the rump. This color varies much as to intensity or dilution ; 

 but is never as dark as the wings. Both surfaces of the wings are deep slaty 

 black: the greater coverts inclining to dark slaty gray: the under surface 

 rather duller in color than the upper ; the prevailing color changing gradually 



* These descriptions of old and young are from specimens in the Philadelphia Academy and 

 Smithsonian Institution. 



1866.] 



