Lepocinclis marssonii is a unicellular, photosynthetic euglenid flagellate in the family Phacaceae, characterized by its rigid, fusiform to ellipsoidal cell body with a distinctive paramylon body as a carbon storage compound. It inhabits eutrophic to mesotrophic freshwater ponds, ditches, and marshes where it contributes to phytoplankton communities. Unlike its genus relative Euglena, Lepocinclis cells have a rigid pellicle that does not allow metaboly (cell shape-changing).