Unilocular foraminifera sculptured in reticular patterns are described. These have relatively short stratigraphic ranges within Argentine Upper Cretaceous and Tertiary sediments. Two types of lagenid forms are distinguished according to their apertural character: a) forms with an elongate and slender neck, generally associated with low energy environments, including Favolagena n. gen. (type species Lagena atilai Bertels) and b) forms with a heavy solid conus and a narrow duct connecting the aperture with the chamber lumen, a thicker wall and coarser surface sculpture. The latter forms are generally associated with shallow, high energy environments, and are herein included in Conolagena n. gen. (type species Conolagena argentina n. sp.). Among foraminifera a reticulate surface pattern occurs relatively frequently in the Cretaceous Nodosariacea and Tertiary buliminids, and could be an important character in reconstructing the phylogeny of unilocular foraminifera. The following taxa are described as new: Favolagena ardolinoi, Conolagena argentina, C. tetratransversa and Conolagena? mateformis.