Gymnodinium sanguineum syn. Akashiwo sanguinea,  Gymnodinium nelsonii, Gymnodinium splendens 

A large dinoflagellate measuring 49um wide, 63um long, with a total volume 79201.13. It is found in warm waters and low to high salinities, 8.9 to 25.0 ppt.This example came from Falmouth Harbor.

Cape Cod