Two species of hysterocinetids occur in the alimentary tract of Drilocrius breymanni, an aquatic oligochaete collected in Departamento del Valle, Colombia. The suckers of both species are unusual for their complexity. In CRATICULOSCUTA escobari gen. nov., sp. nov., the sucker is a shallow oval concavity with longitudinal and transverse supporting elements. About 1/5 of the area of the sucker, in its posterior portion, is ciliated, but argyrophilic puncta-tions, which probably represent kinetosomes, are distributed in a regular pattern over most of its surface. In EPICHAROCOTYLE kyburzi gen. nov., sp. nov., the oval major portion of the sucker is deep, and continuous with a short trough which extends posteriorly and bends toward the left. Veil-like flanges, bordered by a fringe of thick, inactive cilia, arise from the margins of the sucker on either side. In the region of the trough, the flanges may overlap in such a way that the trough is almost completely covered. The trough and a small area of the major portion of the sucker anterior to it are ciliated. However, argyrophilic punctations which probably represent kinetosomes are distributed over most of the surface of the sucker. The pattern of longitudinal and transverse supporting elements found in the sucker itself extends into the flanges. In both Craticuloscuta and Epicharo-cotyle, the arrangement of the adoral and buccal ciliary organelles is essentially like that in Hysterocineta, Ptychostomum, and other ciliates of the family Hysterocinetidae.