The hooded seal (Cystophora cristata) owes its name to the striking nasal appendage that adorns the head of sexually mature males. The wide, fleshy muzzle of adult males usually droops down over the mouth, but when inflated it forms a conspicuous bulbous "hood" on top of the head; a display feature that is often enhanced by the extrusion of an internal membrane through one nostril to form a large, pink, membranous balloon. The face is typically solid black in colour, but the rest of the body's coat is silver or bluish grey, with scattered black spots and blotches. The flippers are heavily clawed, and being a true seal, the broad, hindflippers are extremely efficient in the water, but useless on land, while the smaller, foreflippers have a primary function in steerage rather than propulsion. Owing to their silvery bellies and blue-black backs, hooded seal pups are commonly known as 'blue-backs'.