CLASS II. AYES: OIIDER 8. NATATORES. 303 
HADNTS OF SEA-FOWL^THE GREAT NOilTnEHN DIViiK, GUILLEMOTS, PUFFINS, ETC. 
pressed, and in others long and slender. The mandibles are sometimes sharp and smooth, some- 
times furnished, with denticulations or lamellae at the margins. The texture of the bill also va- 
ries ; but these differences will be referred to in characterizing the families. 
Most of these birds live in societies, which are often exceedingly numerous, inhabiting high 
northern and southern latitudes. Many of them prefer rocky coasts, in the clefts and crannies of 
which they lay their eggs, often on the bare rock, but generally selecting the most inaccessible 
