Pterocystis raineri Siemensma and Roijackers, 1988
Diagnosis: Cell diameter ca. 12 µm. Spine-scales 3.5-7.1 µm long, shaft cylindrical, straight or curved, slightly tapering towards its closed apex, which bears two teeth; basal part of the shaft bends strongly and merges into a more or less circular basal plate, which is 0.43-0.86 µm in diameter. Laterally this plate is connected to the proximal part of the shaft by means of two membranes, thus forming a triangular-shaped hollow, sometimes reduced to a small slit. The plate-scales are oval to slightly ovoid, 2.3-2.8 x 1.3-1.8 µm in size, thin and flat without any marginal rim; central area depressed by a longitudinal ridge, ca. 0.08 µm broad. No other structures were observed.
Remarks: This species is very small. The only species which superficially resembles it is Pterocystis erinaceoides. The latter differs in several aspects from Pterocystis raineri:
- its plate-scales are ovoid;
- the apex of the spine-scales terminates in a sharp point;
- the lateral membranes extend over a fairly long distance along its shaft;
- the bending of the basal part of the shaft is not so abrupt as in Pterocystis raineri.
- the size of P. erinaceoides is twice that of P. raineri, though one must allow for a rather large tolerance in size.
The specific name was given in honour of Dr. H. Rainer.