In September 1965, the Japanese ivory shell, Babylonia japonica harvested from the Ganyudo area of Suruga Bay, Shizuoka Prefecture, caused an outbreak of food poisoning. The causative toxins, designated as neosurugatoxin and prosurugatoxin, were isolated from the digestive gland of the shellfish, and their chemical structures were determined. Pharmacological studies suggested that the toxins have selective affinity for ganglionic nicotine receptors, its affinity constant for these receptors being more than three orders of magnitude greater than that of hexamethonium. Surugatoxin derived from prosurugatoxin was isolated from culture medium of Coryneform bacterium which was isolated from digestive gland of toxic ivory shell, indicating that the origin of the toxins were bacterium.