Ambulacrum (anatomy)

In zoology, an ambulacrum is an elongated area of the shell of an echinoderm in which a row of tube feet are arranged. It is pluralized as ambulacra. The area on the shell between ambulacra is known as an interambulacrum.

Sea urchin shell, or 'test'. Each white band is the location of a row of tube feet; each pair of white bands is called an ambulacrum There are five such ambulacra; the penta-radial symmetry reveals a kinship with sea stars.

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