It includes those invertebrata having the body composed of ringlike segments (arthromeres). By some writers, the unsegmented worms (helminths) have also been included; by others it is restricted to the arthropoda. It corresponds nearly with the annulosa of some authors. The chief subdivisions are arthropoda (insects, myriapoda, arachnida, pycnogonida, Crustacea); and anarthropoda, including the annelida and allied forms.
3. A subdivision of the Crinoidea.