The figs 1&2 could be dinoflagellate cysts as some geometrical opening is observed but not sure. The other two are unidentifiable. All the four figures are definitely not thecamoeba.
I think the both 1st and 2nd image are of empty dinoflagellate cysts and the 2nd one is possibly of Gonyaulax sp. A better angle of the other two could give a better idea.