Morphology and Ontogeny of Phanassymetria Roth

Phanassymetria triserrata Roth and P. quadrupla Roth from the Haragan of Oklahoma are described. The two 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.