Conrad, T. A. (1849). Descriptions of new fossil and Recent shells of the United States. <em>Journal of the Academy of Natural Sciences of Philadelphia.</em> (2) 1(4): 207-209., available online athttps://biodiversitylibrary.org/page/35780297 page(s): 208; note: as D. protracta[details]
original descriptionConrad, T. A. (1849). Descriptions of new fossil and Recent shells of the United States. <em>Journal of the Academy of Natural Sciences of Philadelphia.</em> (2) 1(4): 207-209., available online athttps://biodiversitylibrary.org/page/35780297 page(s): 208; note: as D. protracta[details]