Clam breath, LH. It's the source of Mustard Gas. When the clam shells are closed they fill up with the gas. During WW1 people fired the gas-filled clam shells at each other using trebuchets and ballistae. The other side would find the clam shells and pry them open to make chowder, which of course released the deadly gas inside. It's really clam breath; you only think it's 1,5-dichloro-3-thiapentane.