Weaver & Palmer. 1922. Fauna from the Eocene of Washington. University of Washington Publications in Geology 1(3): 1-56. https://www.biodiversitylibrary.org/page/17201643#page/11/mode/1up.
Weaver & Palmer, 1922. Univ. Wash. Pub. Geol. 1(3): 14, pl. 10, fig. 10.