Note: They have a more or less elongated body, often
flattened beneath, and a circle of tentacles, which are
usually much branched, surrounding the mouth; the skin
is more or less flexible, and usually contains
calcareous plates of various characteristic forms,
sometimes becoming large and scalelike. Most of the
species have five bands (ambulacra) of sucker-bearing
feet along the sides; in others these are lacking. In
one group (Pneumonophora) two branching internal gills
are developed; in another (Apneumona) these are
wanting. Called also {Holothurida}, {Holothuridea}, and
{Holothuroidea}.