2. (Zo["o]l.) A large, ornamental, marine, univalve shell of
the genus {Melo}.
{Melon beetle} (Zo["o]l.), a small leaf beetle ({Diabrotiea
vittata}), which damages the leaves of melon vines.
{Melon cactus}, {Melon thistle}.
(a) (Bot.) A genus of cactaceous plants ({Melocactus})
having a fleshy and usually globose stem with the
surface divided into spiny longitudinal ridges, and
bearing at the top a prickly and woolly crown in which
the small pink flowers are half concealed. {M.
communis}, from the West Indies, is often cultivated,
and sometimes called {Turk's cap}.
(b) The related genus {Mamillaria}, in which the stem is
tubercled rather than ribbed, and the flowers
sometimes large. See Illust. under {Cactus}.