The body is typically covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump in the members of the phylum

The body of molluscs it unsegmented and is divided into a distinct head, muscular foot and visceral hump. It is covered by a calcareous shell. The body of hemichordates is divided into proboscis, collar and trunk. The body of arthropods is mostly divided into head, thorax and abdomen. The body of annelids and arthropods is metamerically segmented.