What is "selkirkia"

Selkirkia is a genus of predatory, tubicolous priapulid worm known from the Middle Cambrian Burgess Shale, Ogygopsis Shale and Puncoviscana Formation. In the Burgess Shale, 20% of the tapering, organic-walled tubes are preserved with the worm inside them, whereas the other 80% are empty (or sometimes occupied by one or more small agnostid trilobites). Whilst alive, the tubes were probably vertical, whereas trilobite-occupied tubes are horizontal.