Reexamination and serial sectioning of the type material of Reticularia septentrionalis Whiteaves 1904 and Meristina expansa Whiteaves 1904, from the Silurian (upper Llandovery) Attawapiskat Formation, Ekwan River, Hudson Bay Lowlands, indicate that they belong to the same species and that they can be assigned to the genus Pentameroides. These described species are also identical to Sapelnikovia [=Reveroides] norfordi Boucot and Johnson 1979, from the same formation on the Attawapiskat River nearby. All three species are thereby assigned to a single species, Pentameroides septentrionalis. The inflated shell of this species ranges from smooth and nonlobate to bisulcate–bilobate and rarely weakly trisulcate. This morphology is thereby viewed as a species-specific character, leading to the conclusion that Reveroides Sapelnikov 1976 is probably a junior synonym of Pentameroides.