Jim Ure, Bait for trout, being the confessions of an unorthodox angler, Chicago, Henry Regnery compazny, 1973, p. 73.
This is the one we call the « rockroller ». elsewhere it is called rockworm or periwinkle. It imbeds itself with a hard, shelllike mosaic of tiny rocks. The juicy worm is neatly tucked inside this bit of armorplate.