All the Cephalopoda, without exception, are marine. Some of the Cuttle-fishes (such as the Octopi and Sepia) live in the vicinity of land, especially frequenting rocky bottoms; while others (such as Argonauta, Spirula, Sepiola, Onychoteuthis, etc.) live in the open sea, often far from land, swimming at or near the surface. Some of the Cuttle-fishes attain a gigantic size; but all these colossal forms of the class appear to belong to the Decapoda. The Architeuthis of the North Atlantic is certainly known to attain a length of 15 feet or upwards to the body and head, and from 30 to 40 feet or more in the long tentacles. The Pearly Nautilus is confined to the Pacific and Indian Oceans, and appears to be an inhabitant of shallow water.