LESTRIS. 
263 
under-parts, are greyish black, tinted with brown 
on the belly, and on the chin paler, nearly dark- 
grey ; the quills and tail are black ; the greater and 
lesser wing-covers grey, the latter tipped with 
greyish white, which shows a pale bar across ; the 
last rump-feathers, part of the tail-covers, and a 
limited spot behind each thigh, white ; tarsi, feet, 
and bill, black. 
These are all the birds belonging to the Petrels 
which have yet been found on our islands ; but it is 
possible that others of this small race may yet have 
been overlooked, more particularly as the real range 
of the last has been seen to be so far distant. They, 
with one or two allied genera, are by far the most 
decidedly sea-living birds among the Laridas. 
Our next form also spends a great portion of its 
time on the ocean, has a powerful flight, exhibits 
some alliance with the last in the structure of the 
feet, and is remarkable in pursuing the true gulls, 
and forcing them to disgorge or quit their newly- 
taken prey. It constitutes the 
Genus Lestris, Tlliger. — Generic characters . — 
Bill strong, thick, compressed at the tip, co- 
vered as far as the anterior angle of the nos- 
trils with a horny cere ; tip of maxilla finishing 
in a powerful hook ; mandible with a strong 
angle, fitting into the maxilla ; nostrils lateral, 
placed immediately behind the tip, angular, an- 
teriorly widest, pervious ; wings long, first quill 
