We present here descriptions and light and scanning electron micrographs for four species of Frustulia. Two of the species, F. rexii and F. cf. saxonica, were collected from the northern portion of the lower peninsula of Michigan, U.S.A. The third, F. cf. krammeri, can be found on at least two islands in Hawaii, U.S.A., while the fourth, F. lacrima, was collected from lakes in Brasil. We refer to the four species as “typical” Frustulia because their longitudinal rib systems resemble that seen in the generitype, F. saxonica Rabenh., and they share other valve features with this group. The new species differ from congeners in valve shape, organization and density of the striae, and degree of physical integration between the longitudinal ribs and helictoglossae. In both well-studied (Michigan) and less-studied (Hawaii, Brasil) parts of the world it appears there is more work to do to document the diversity of the genus Frustulia.