Pterocystis paliformis (Dürrschmidt, 1987) Siemensma, 1991
Diagnosis: Periplast 8-15 µm in diameter (measurement based on whole mount); details of protoplast unknown. Scales of two types. The spine scales are almost spade-form, 4.5 µm long and max. 2.3 µm breadth. The shaft is reduced to a short hollow ridge of varying breadth, ending distally with a blunt apex. The lateral wings and the basal wing are narrow rimmed and joined to the spade-like form of the spine scales. The wings on either side of the shaft run almost parallel to it but then narrow abruptly and terminate sub-apically. The area around the “shaft base” is depressed to a concavity. The plate scales, 2.5 X 1.5 µm, are elliptical or ovoid. The scales are thin and narrow- rimmed. The central swelling is rudimentarily developed and slightly shifted to the smaller pole of the scale.
Remarks: A. paliformis is conspicuous by virtue of the remarkable similarity between the plate and spine scales. It appears that the structure, which forms the shaft in the spine scales might be identical with the central swelling in the plate scales. Other corresponding points are the concave depression at the basal end of the shaft and the way the width of the shaft and the central swelling varies in both scale types.
Distribution: Chile, New Zealand.