Barrufeta Sampedro and Fraga 2011  

From Sampedro et al. 2011:

Unarmored dinoflagellates occur with peridininas the major light-harvesting accessory pigment. Anapical groove that starts in the anterior part of theintersection between the sulcus and the cingulum,runs diagonally to the anterior right side of the cell,and then turns counterclockwise around the apicalpart of the cell in a very elongated transversal loopbefore ending near the right side of its origin.

Unarmored dinoflagellates occur with peridinin as the major light-harvesting accessory pigment. An apical groove that starts in the anterior part of the intersection between the sulcus and the cingulum, runs diagonally to the anterior right side of the cell, and then turns counterclockwise around the apical part of the cell in a very elongated transversal loop before ending near the right side of its origin.