Tabellaria is a genus of freshwater diatoms.
[1] They are cuboid in shape, and the frustules (siliceous cell walls) are attached at the corners so that the colonies assume a zigzag shape.
"SEPARATING TABELLARIA BACILLARIOPHYCEAE SHAPE GROUPS BASED ON FOURIER DESCRIPTORS" (PDF).
Proceedings of the Academy of Natural Sciences of Philadelphia.
"The Diatom Genus Tabellaria: I. Taxonomy and Morphology".