Guide to Tibetiella

SPECIES OF TIBETIELLA ARE NOT KNOWN TO OCCUR IN NORTH AMERICA

Cells are linear-elongate with capitate apices. Valves are heteropolar in valve view and nearly rectangular or trapezoidal in girdle view. Striae are uniseriate and parallel, but may be radiate near the apices. The sternum is narrow, expanding to a rectangular central area. Two to five rimoportulae are present at each apex, positioned adjacent to the sternum. The external openings of the rimoportulae are elongated, while the internal openings have extended lips. A distinct apical porefield, or ocellulimbus, is present. Striae are arranged in less organized manner than in the genus Ulnaria. Spines may be present along the valve margin. The cingulum is composed of a series of bands. Each band each possesses a longitudinal row of elongated poroids near the pars interior.

Two species of Tibetiella have been described, both from epilithic habitats of slow-flowing reaches of the River Nujiang, in Tibet. It was found growing with rheophilic taxa, including Hannaea arcus, Meridion circulare, and Achanthidium sp.