Guide to Dickieia

Valves are lanceolate, linear-lanceolate, or elliptic-lanceolate, often with protracted ends. The valve face is strongly curved onto the mantle, which is relatively deep. As a result, cleaned frustules often come to rest in girdle view. A fascia is present and is interrupted at the margins by short, widely-spaced striae. These short striae may not be visible in valve view. Striae are composed of small round poroids, occluded internally by hymenes. External proximal raphe ends lie in spatulate grooves; the raphe ends are deflected slightly to one side. Terminal raphe fissures are hooked toward the secondary side of the valve. A single-lobed chloroplast contains a prominent, central pyrenoid. Cells are encountered both solitary and in macroscopic, blade-like mucilaginous colonies.

Dickieia is epipelic in marine and brackish waters. In non-marine waterbodies the preference for high conductivity waters distinguishes Dickieia from Stauroneis. Dickieia is further distinguished by having only one chloroplast, not two as in Stauroneis. In North America, it has been reported from streams on the northwestern Great Plains and coastal Prince Edward Island, Canada.

The genera Staurophora and Dickieia were recently combined and the latter name has priority (Cox 2026). The two genera were described by different authors - focusing on different features, or not appreciating gradation in a given feature: Berkeley and Ralfs (1844) focused on a central area with widely-spaced striae in Dickieia ulvaceoides. Mereschkowsky later focused on chloroplast structure and central area with much less visible and shorter central area striae in Staurophora (Mereschowsky 1903). Taxa from both of these genera show strong overlap in valve and organellar morphology, including ultrastructural features now visible with SEM. They also have strong autecological overlap, preferring high salinity, epipelic habitat along the coast and in inland streams.

The page for Staurophora on this website is now closed (2026).