Mastogloia Pumila Guide
Credit: Loren Bahls
  1. Lateral sterna present
  2. Central partecta larger than distal partecta
  3. Striae uniseriate
  4. Raphe straight

Valves are linear-lanceolate to elliptic-lanceolate with subtly protracted and broadly rounded apices, lateral sterna, and partecta of two different sizes. The striae are uniseriate and the raphe is straight, rather than sinuous.