Figure 3. a–l. Protoperidinium curvicorne comb. nov. – a and i (PC), b and j (Epi), and e (SEM): cell in ventral view showing round and broad body with the long apical and antapical horns, the wide 1’ plate, descending cingulum, the deep sulcus with two sulcal lists; – c (PC) and k (Epi): cell in left and right lateral view respectively, showing curved cell relative to the longitudinal axis by the apical horn strongly tilted forward, dorso-ventrally compressed cell and strongly oblique cingulum; – d and l (Epi): cell in dorsal view; – f (SEM): a part of the epitheca in ventral view showing the surface of the theca is slightly smooth and two kinds of pore sizes (arrow and arrowhead); – g (DIC, Lugol’s stain): the 1’ plate with pores (arrowhead); – h (Epi): cell in the dorsal view showing the epithecal plates. The scale bar in Fig. a = 50 μm applies to Figs b–e and h–l. Figs a–g were collected from Vietnamese coastal waters, and Figs h–l were collected around Hormuz Island (Persian Gulf, Iran).