Observations by aedrahos

scale bar in image is 10 μm

Cruciform valves with widely spaced, distinct striae. The axial area is lanceolate. The apices are not as wide as the transapical protrusions. The transapical protrusion are sometimes slightly off centered, creating transapical asymmetry. The location and width of the transapical protrusions are variable among individuals of this species.

in observed specimens,
length range = 16-21 μm
width range = 12-13.5 μm
striae density range = 9-10 per 10 μm

scale bar in image is 10 μm

Tri-lobed valves with an expansion in the center and both apices. The distil expansions are triangular and the central expansion is more circular. . There is a characteristic constriction just before the swelling on the apices. Near the central area is one large rimoportula. The sternum is thin. This species differs from T. flocculosa because it lacks marginal spines and has a smaller/no axial area

in observed specimen,
length range= 89-92 μm
width range = 7-8 μm
striae density range = 18-19 per 10 μm

this species was rare in my sample, so only two were observed.

scale bar in image is 10 μm

linear valves with protracted ends and a very shallow and wide constriction in the middle. The central area is rectangular to bowtie shaped with a small circular depression in the center. The axial area is linear-lanceolate. Size of the central area is variable among species. The proximal raphe ends are bent, and the distal raphe ends have a rounded hook going the opposite direction of the proximal raphe. The striae are radiate in the center, but become convergent at the poles. This differs from the nominate variety due to a smaller width range due to the slightly constricted central area.

specimen of this species were very rare in my sample, so only one was observed.