Diagnostic characters: The cross-furrow is above the center of the
body, and its edges, as well as the left edge of the longitudinal
furrow, are usually produced into characteristic ledges; those of
the cross-furrow usually form great funnel-like anterior processes,
while those of the longitudinal furrow usually form great, lateral,
wing-like processes ornamented by ribs and other markings.
1. Without shell; longitudinal Genus *_Amphidinium_
furrow may open & close
2. With shell; longitudinal furrow 3
unchangeable