FIGURES 217–222 in Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser

FIGURES 217–222. Scanning electron micrographs of Trilamina nitescens from Oamaru, New Zealand. Fig. 217: Oblique external view of a valve with attached valvocopula (VC). Fig. 218: Detail of the specimen in Fig. 217, showing the hyaline depressed sectors next to the valve centre. Arrow points to a poroid which might represent an external opening of a rimoportula. Fig. 219: Detail of the specimen in Fig. 217, showing the inconspicuous polar pseudocellus (arrowhead). Fig. 220: Flat internal view of a specimen with an attached valvocopula. Internal opening of the rimoportula is indicated by the white arrow. Arrowhead points to the prominent, tapering costa on the underside of the depressed area. Black arrow indicates the costa associated with the margin of the valve centre. Fig. 221: Oblique internal view of the specimen in Fig. 220, showing the differentiated clasping devices on the valvocopula. Large clasping mechanism is indicated by the arrowhead; small clasping mechanism is indicated by the white arrow. Note that the possible pseudocelli are bound by costae on the interior (black arrows). Fig. 222: Detail of the small clasping devices attached to the internal costae in the distal part of one of the projections.