Sides of mandible without longitudinal groove. Tail short and rounded. Southern Ocean and N. Pacific Ocean.
(i.) Interscapular region and mid-bach white.
D, exulans. 42". Legs flesh. Bill yellow. Head white. Upper back with narrow transverse dark lines. Wing-coverts slaty black. Primaries black. Under-wing and axillaries white. Tail white, irregularly marked on both webs near tips. Southern Ocean, Cape seas, S. Atlantic, and S. Pacific to New Zealand. Young brown, face white.
D. regia. 48". Similar to D. exulans, but without transverse dark lines on back. Wing-coverts dark grey. Tail white, without marks. New Zealand. Young white.
D. chinoptera. 48". Similar to D. regia, but wing-coverts nearly white. A large white patch on inner web of under surface of primaries. Southern Indian Ocean.
D. albatrus. 37". Legs dark. Bill yellow. Head buff. Crown, nape, and back of neck tinged buff. Scapulars, wings, and end of tail grey-black. A large white patch near distal end of humerus. Shafts of primaries and of tail yellowish white. N. Pacific Ocean. Young sooty brown.
(ii.) Interscapular region and mid-back brown or black.
D. irrorata. 35". Legs dark. Bill yellow, tip dusky. Head and neck white. Back, wings, and tail sooty. Above freely mottled and barred white. Below sooty, freely mottled and freckled white. West coast of Peru.
D. nigripes. 28", Legs black. Bill red-brown. Above sooty brown. A large triangular spot behind and below eye. Below sooty. Tail white at the base. N. Pacific Ocean.
D. immutabilis. 32". Legs pink. Bill grey, tip black. Head, neck, rump, upper tail-coverts, and under surface white. Back, wings, and end of tail sooty. Under wing-coverts brown and white. Laysan Island and vicinity.
D. melanophrys. 30". Legs yellow. Bill yellow, tip darker. Plumage white. Short black band on either side of eye. Back and wings black. Tail slate-grey, shafts white. Southern Ocean, straying to N. Atlantic.
D. bulleri, 34". Legs red. Bill yellow, sides slaty. Above sooty. Below white. Tail dark grey-brown. New Zealand.
Also the genus Thalassogeron. Sides of mandible without longitudinal groove. Tail rounded. Six species, viz.—
T. culminatus. 36". Legs yellow. Bill, culmen yellow, sides black. Head and neck whitish grey, A dark patch in front of and above the eye. Above sooty. Rump and under surface white. Tail dark grey, shafts white. Southern Oceans, ranging to Pacific coasts of C. America.
T. chlororhynchus. 33". Legs flesh colour. Like T. culminatus, but with an indistinct grey mark in front of the eye. Southern Oceans.
T. eximius. Similar to T. chlororhynchus, but lower mandible is black. No dark spot behind eye. S. Atlantic Ocean.
T. cautus. 35". Legs grey. Bill, culmen yellow, sides grey. Head, neck, lower back, upper tail-coverts, whole under surface, under wing-coverts, and axillaries white. A greyish black mark in front of the eye. Back, wings, and tail ashy. Tasmania.
T. salvini. 38". Similar to T. cautus, but forehead and crown more grey. New Zealand.
T. layardi. Allied to T. cautus. Cape seas.
Also the genus Phoebetria. Sides of mandible with a deep longitudinal groove. Tail long and cuneate. One species— P. fuliginosa, 36", legs hazel, bill black, groove orange, plumage sooty, white ring round eye, Southern Oceans. (B.M. Cat., xxv. 440-455.)