196 
ON TUB OLASSItTCATION OF BIRDS. 
a fourth : they skim over the surface of the ocean 
with great swiftness, and scoop up small marine insects 
and other animals. The true, or typical, gulls 
(Lm-m) are a numerous race, dispersed in every clime, 
and so closely resembling each other in plumage, that 
many of the species are even now but imperfectly 
understood ; they bear a close resemblance, in general 
appearance, to the terns, but the bill is stronger, and 
the upper mandible much more curved towards the 
end : many are of large size ; and all are voracious 
devourers of fish, and of every marine animal, dead or 
alive, which is cast upon the shore : they particularly 
abound in northern latitudes, but seem to range over 
the whole world of waters. The parasitic gulls 
(Lestrh) are the raptorial representatives, and are 
almost confined to cold regions : they are known by 
their stronger conformation, their different shaped bill, 
and the rough scales upon their feet ; these birds, like 
the frigate cormorants, derive their chief supply of food 
by robbing their more feeble congeners ; they pursue 
the largest gulls, and make them disgorge or relinquish 
their hard-earned game. The black-toed and the arctic 
gulls belong to this group, and both are occasionally 
seen on the northern shores of Britain. 'I'he genus 
Biomedia includes the well-known and gigantic alba- 
trosses, the most powerful and bulky of the whole 
fanuly ; they are oceanic birds, living almost constantly 
out at sea, but are more particularly abundant in the 
Pacific Ocean : we have no examples in Britain, or, 
indeed, in Europe : the extent of tlieir outsjiread wings 
is enormous ; yet their flight, except in stormy weather, 
is by no means lofty : like all the rapacious birds of 
the ocean, they are most voracious, and their flesh is rank 
and repulsive. The genus Hnladroma comprises such 
of the albatrosses as have the bill more resembling that 
of the petrels, while they agree with the former in 
being destitute of a hind toe ; but only one or two 
species have as yet been clearly ascertained. The true 
petrels (rrocelluria) have the lower mandible trunc- 
