Plagiopyxis pentagonostoma Bartos, 1963

Diagnosis: The large oblong-oval shell, built of larger fragments of minerals, has much larger structural material on the dorsal side, and especially at the posterior end, than on the rest of its surface. The building material is glued together with organic cement, giving the shell a light to deep yellowish brown coloration. On the whole the shell is very similar to that of Plagiopyxis labiata, with the difference being the thickness of the shell, which in the new species is very small, while in P. labiata it is only a little smaller than the width of the shell. The front edge of the shell opening is 22 µm away from the shell front end. The shell opening is pentagonal with broadly rounded corners and it is always directed with one of its corners forward. The opposite side forms the rim where the ventral side of the shell ends. From this edge, the ventral side merges into a broad, tongue-shaped, rounded, triangular outgrowth, which, directed forward, clearly inclines towards the interior of the shell opening. In this respect, too, the new species is very close to P. labiata. Viewed from the side, the shell is low, broadly rounded in front and behind, and the dorsal and ventral surfaces are flat to parallel.
The shell opening with its front edge is 22 µm from the anterior end of the shell, it is 35 µm high, its posterior margin measures 28 µm, just as wide is the base of the tongue-shaped outgrowth, which protrudes 21 µm obliquely forward into the shell opening.

Dimensions: Length 124 µm; width 100 µm; dorso-ventral (height) 42 µm.

Ecology: Mosses. Java, Indonesia.