{55}The horny sheath of the maxilla is composed of from three to five more or less distinct pieces, while the powerful bill may be long, thin, and slightly decurved, as in _Aptenodytes_ and _Pygosceles_; shorter and pretty broad, as in _Eudyptes_; or very stout, short, and compressed, as in _Spheniscus_, where the prominent hook of the culmen overhangs a truncated mandible. The three metatarsals are not completely fused as in other birds (p. 10), the scutellated metatarsus itself being shorter and broader than in any other Family, except the Fregatidae; the legs are set far back, the tibia is hardly visible, and the short thick toes are directed forwards, the small hallux alone having no web. Even more striking are the wings, which are totally devoid of normally-developed quills, though the number of feathers is very large, the primaries themselves amounting to about thirty-six; these flippers or paddles have highly compressed bones with no power of flexure, but work freely from the shoulder in rotatory fashion, requiring a corresponding increase of strength in the muscles of the neighbouring parts. The numerous rectrices are fairly long and stiff in _Aptenodytes_, _Pygosceles_, and _Eudyptes_, but shorter in _Spheniscus_, having considerably reduced vanes. On the body we find no naked tracts, but a uniform covering of small scale-like feathers, with or without barbs, and an equally uniform distribution of down both in adults and young; the moult, moreover, is accomplished in an exceptional manner, the plumage being shed in masses, and that of the wing gradually flaking off above the new coat. The process apparently occupies about ten days.[53] Long superciliary crests occur in _Eudyptes_, the mandible is more or less feathered in _Aptenodytes_ and _Pygosceles_, and the metatarsi are clothed besides in _A. forsteri_. The furcula is U-shaped, the syrinx tracheo-bronchial, the tongue rudimentary, an after-shaft is present, and the plentiful subcutaneous fat produces a marketable oil.