Death Crab would have been almost as evocative a genus name as Hallucigenia, but it's Nectocaris (swimming crab), not Necrocaris. This is another Burgess Shale mystery creature which has since found a taxonomic home with the lovely cephalopods.
Disclaimer: This model of Nectocaris is not designed to be used as marijuana paraphernalia. It has no mouth and anus to be exploited as an airway. It's not anatomically correct. As for Nectocaris #3, however...