Synedrosphenia parva sp. nov. A holotype from Guam in LM, arrow indicates annulus near valve face–mantle junction (GU75A-4) B, C valve in external view (SEM), basal and apical poles, respectively, arrow indicates annulus (GU75A-4) D, E internal views of apical and basal poles, respectively, arrows indicate pseudoseptum (J5) F, G frustule in girdle view, apical and basal portions, respectively, showing the girdle bands including the large apical cap of the pleura, smaller at the basal pole and perhaps not connected (arrowhead in G indicates the apparent end of the pleura); arrows on F, G point to polar notches (GU75A-4). Scale bars: 25 µm (A); 10 µm (B, C, F, G); 5 µm (D, E).