Thalassiophysa hyalina (Grev.) Paddock et Sims
The apical axis is about 50-90µm, and the pervalvar axis is about 35-55µm (Fig. 3, LM phase contrast; apical axis is 63µm). Striae are not visible in the light microscope, and they appear as indistinct poroids in SEM, numbering about 75 in 10µm (barely visible in Fig. 2). It is a fairly common benthic species throughout the IRL, but never abundant. It has a worldwide distribution in coastal bays and estuaries, from the tropics to boreal regions.
Cells solitary, almost always found in girdle view (Fig. 1, living cell, arrow indicates incised raphe; arrowheads indicate cytoplasmic threads. Apical axis is 54µm). The valves are flattened, keeled, and incised in the middle. The raphe system curves into the ventral side near the center (Fig. 2, detail of central raphe area, SEM). There is one flattened chloroplast per cell, oriented in the pervalvar axis, appearing suspended in the cell interior by a series of cytoplasmic threads (Fig. 1, arrowheads). Paddock & Sims (1980; as Proboscidea) and Round et al. (1990) discussed the cell structure in detail.
Paddock B, Sims PA. 1980. Observations on the marine diatom genus Auricula and two new genera, Undatella and Proboscidea. Bacillaria 3: 161-196.
Round FE, Crawford RM, Mann DG. 1990. The Diatoms. Cambridge University Press, Cambridge (U.K.). 747pp.