To the preparation of this summary the author has brought the results of more than 50 years' study of the molluscan fauna of the northwest coast, his personal investigatons in the field having begun in 1865, when, under the auspices of the Smithsonian Institution, he visited the shores of the Pacific as a member of the scientific corps of the Western Union Telegraph Expedition. SInce that time a constant inflow of material from that region has enriched the collection of the United States National Museum until it has become unrivaled in this group of animals.