Genus Penardiophrys Mikrjukov, 2000
Diagnosis: desmothoracids enclosed by capsule composed of jointed polygonal facets; each facet bears a minute pore.
Remarks: Mikrjukov designated this genus to include Hedriocystis reticulata Penard 1904 and H. spinifera Brown, 1918. In 1997 Mayer describes H. spinifera with "numerous facets, with high edges (...). In the centre these facets have a number of small granules which look like pores." These granules, which I also could observe, are described by Brown as fine pores. However, it is very doubtful that Brown could see the difference between granules and pores concerning the very small size of the specimens (8-20 um) and the lack of DIC microscopy in his time.
In 1968 Rainer had described Belonocystis tubistella, a species that closely resembles H. spinifera. Nicholls (2012) published TEM images of the fine structure of the scales of B. tubistella. He doesn't consider B. tubistella as identical with H. spinifera, because "when Rainer (1968) established Belonocystis, he was well aware of the spined Hedriocystis spinifera Brown, 1918 (...) and included drawings reproduced from Brown€™s original publication." I do not agree with Nicholls that both species are clearly different. If one compares the original drawings of Brown with the drawing of Mayer and recent photomicrographs, it is not difficult to see the agreement between both species.
However, the description of Penardiophrys excludes H. spinifera, because this species has no capsule but loose scales, which can detach from the cell, which I have observed several times. It is correct to transfer H. spinifera to the genus Belonocystis, considering B. tubistella als a junior synonym.