What is the structure found in the collar region of Hemichordates?

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Hemichordata was earlier considered as a sub-phylum under phylum Chordata, but now it is placed as a separate phylum under non-chordata. Hemichordates have a rudimentary structure in the collar region called stomochord, a structure similar to notochord. Animals belonging to the phylum Chordata are bilaterally symmetrical, triploblastic, coelomate with organ-system level of organisation. Animals belonging to phylum Chordata are fundamentally characterised by the presence of a notochord. They (Members of Phylum Chord