Primitia
Distinguished from Primitiella by having a well-marked subcentral, usually curved sulcus with undefined swellings or low nodes on one or both sides of it instead of an undefined depression. As a rule also the valves are shorter, the outline being generally more ovate (Bassler and Kellett, 1934).
Species
Primitia lativia Ulrich, 1889
Occurrence: Whitewater
Reference: Dalvé, 1948; Bassler and Kellett, 1934
Primitia milleri Ulrich, 1890
Occurrence: Liberty
Reference: Dalvé, 1948; Bassler and Kellett, 1934