THE occurrence of the American oyster-drill, Urosalpinx cinerea Say, on oyster beds in the River Blackwater, Essex, was recorded in NATURE (Aug. 18, 1928, P. 241), and has since been found to be present in great numbers on the shallower parts of these beds in summer-time. This pest, which was first confused with the rough tingle, Ocinebra erinacea (= Murex), has thus become acclimatised, like its congener, the American slipper-limpet, Crepidula fornicata, since its introduction from America, and unless care be taken may spread to other oyster-beds. There now occur in England three oyster-drills or tingles, which in the adult state bore holes through the shells of oysters—and other organisms—and devour the body of the prey through the hole made in the shell, namely: