Octopus is the common name for all 8-armed cephalopod molluscs; it more properly refers to the largest genus in order Octopoda (over 100 species). Octopuses are also called devil fishes for the "horns" (cirri) behind their eyes, but the image of an 8-legged cat is more apt. They have large slit eyes and explore the sea bottom with catlike intelligence, pouncing on prey, eg, crabs. Canada has 2 of the world's largest octopods: the Pacific Octopus dofleini, a slow but typical benthic (bottom-dwelling) hunter that may exceed 80 kg; and the Atlantic Alloposus mollis, which floats in the plankton like a 40 kg jellyfish. There are 9 smaller species. The paper-thin "shells" of the octopod Argonauta (paper nautilus) occasionally drift to Canadian shores from the tropics. Not true shells, they are boatlike nests secreted by the female and used by her as a brood chamber and retreat.