What is "mackenzia"

Mackenzia is an elongated bag-like animal known from the Middle Cambrian Burgess Shale. It attached directly to hard surfaces, such as brachiopod shells. Mackenzia was originally described by Charles Walcott in 1911 as a holothurian enchinoderm. Later, Mackenzia is thought to be a cnidarian and appears most similar to modern sea anemones.