HALOB^NA C^RULEA. 35 



Bill black ; upper mandible sharply hooked, lower much flattened at 

 its base. 



Nostrils tubular, divided by a septum, looking upward and placed far 

 back on the bill. 



Iris very dark-brown or black ; not visible during life. 



Head slaty-blue on top and at back, shading iijto paler slate-color at 

 the sides. Throat and parts around insertion of bill white, the slate- 

 tint nearly meeting, from each side, under the throat. 



Breast, belly, and under parts of wings and tail white ; upper surface 

 slaty-blue, shading into very dark tint; mottled with brown along prima- 

 ries, secondaries, and tertiaries. Narrow white band, of one-half inch, 

 at extremity of tail. The dark tint above mentioned runs from the 

 carpal joint of either wing downward to the rump, making, when the 

 bird is flying, a V-shaped marking, not so distinct, however, in this 

 species as in Pseud oprion. 



Tarsus and foot black and scutellated (excepting No. 41, a very pale 

 specimen, taken with the egg, in which they were noted as pearl-gray). 



Claws black, the middle claw being turned sharply outward. 



Upon first landing (September 13), the hill-sides, apparently quite 

 deserted during the day, became at night perfectly alive with these 

 birds and a species of Pehoanoides (P. urinatrix, Gm.), flying irregularly 

 about the rocks and hummocks of Azorella, and filling the air with their 

 call. The note much resembles the cooing of pigeons, consisting of 

 three short notes repeated in rapid succession and followed by two long 

 ones, thus : " kiik-kiik-kiik — coo-coo." They seemed rarely to» fly over 

 the water, but to confine themselves to the neighborhood of their bur- 

 rows, sometimes alighting and again taking wing — very much as if there 

 were legions of bats inhabiting the hill. I never succeeded in satisfy- 

 ing myself as to the object of this constant flight during the night, 

 although I spent much time in watching them, since, so far as my obser- 

 vation extended, there were no night-flying insects whatever upon the 

 island, nor did the structure of the stomachs of these birds seem fitted 

 to an insect diet. 



The burrows are excavated beneath the mounds of an umbelliferous 

 plant, which abounds on the Kerguelen hill-side {Azorella selago, Hook, 

 fil.), growing in dense masses of often several feet in diameter. The 

 holes usually run straight inward for a foot or more, then turn sharply 

 to the right or lett, parallel with the hill-side, thence downward, often 

 doubling once or twice upon themselves and communicating with other 



