Guide to Mastogloia binotata
- Partectum single, rectangular
- Fascia narrow, lanceolate
- Valves broadly elliptic
- Areolae distinctly punctate
The presence of a centrally located single partectum on each side of the valvocopula is unique, and therefore, a diagnostic feature of the species. In the absence of an attached valvocopula, the broadly elliptic valve outline, the narrow lanceolate fascia, and distinctly punctate areolae arranged in a crossed pattern help to further distinguish the species.