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Abstract
The diatom order Rhaphoneidales is characterized by high generic diversity and low species diversity. Several of the genera defy traditional centric/pennate morphological distinctions. All of the genera within this order are neritic marine, and most are epipsammic. Most are known to have long stratigraphic ranges. Four genera within the family Rhaphoneidaceae are discussed, including Diplomenora Blazé, Detonia Frenguelli, Adoneis Andrews & Rivera and Dickensoniaforma gen. nov., described herein. Dickensoniaforma includes two species, both new: D. arctica sp. nov. and D. navicularia sp. nov. The new taxa occur in Paleogene (lower Tertiary) deposits in the Norwegian—Greenland Sea. No extant examples of Dickensoniaforma are known.