Phanassymetria triserrata Roth and P. quadrupla Roth from the Haragan Formation [Devonian] of Oklahoma are described. The 2 forms are considered distinct species. Early instars of both species are identical and separation cannot be made until the fourth instar. The trough in the left valve of P. triserrata reflects some internal structure. Although it may be a sex feature, it is not a dimorphic character.

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