An unpublished monograph on New York Land and Fresh-Water mollusks, with accompanying original watercolor and black and white drawings and correspondence about them. During the first decade of the century the New York State Museum employed Pilsbry to prepare this work. It contains over 1200 pages of typed text and the original hand-written copy, 67 colored plates, 58 pencil or ink plates, and over 300 text-figures. The colored plates, mostly by Helen Winchester, although some are by Pilsbry who learned the technique from her, and scattered figures by Pilsbry, Barkentine and W. P. Davison are unusually fine. It is understood the paper was not then published because of lack of funds. Published in part in 1997.