Of all sea-birds, the Petrels are the most pelagic. They are the birds of the wide ocean, even showing small partiality for narrow seas, and chiefly frequenting for breeding purposes only such spots as face the widest expanses of water. They are the most marine of birds, yet they form one of the least apparent features in the bird-life of the sea, and more especially when that bird-life is studied from the coast. Their crepuscular, or nocturnal, habits during their short visits to the land to breed, their sombre hues, their low flight, just above the waves, all combine in rendering these birds exceptionally difficult of observation. The Petrels present such exclusively distinctive characters that many systematists relegate them to an order by themselves. This order is termed Tubinares, because the birds contained in it have the nostrils tubular—a character which serves, at a glance, to distinguish a Petrel from all other species. Other external characters are their hooked beak, webbed feet, and long wings. More than a hundred species of Petrels are known to science, which are dispersed throughout the seas and oceans of the world. The young, as far as is known, are hatched covered with down, but they remain in the nest until capable of flight. These birds moult once in the year. None of the species are very remarkable for bright colouration, although, in some, the colours—brown, black, gray, and white—are strongly contrasted. Several species of Petrel wander occasionally to the British seas, but only four species breed within our area, and of these we now propose to treat. FULMAR PETREL.