Agassiz, L. 1850. Catalogue of shells, with descriptions of new species [pp. 243-245, by A.A. Gould]. Lake Superior: Physical Character, Vegetation, and Animals, compared with those of other and similar regions. 428 pp. https://www.biodiversitylibrary.org/item/72194#page/11/mode/1up.
Gould in Agassiz, 1850. L. Superior: 245, footnote.