An investigation of some faunas rich in Milaculum Müller, 1973 lead to the conclusion that the Milaculum animal was - at least partly - covered by plates of different morphology. Several specimens of Milaculum were encountered with adhering smaller platelets showing that the epidermal tissue of this animal consisted of a mosaic of larger and smaller plates. The characteristics of the material encountered are suggestive of an agnathan affinity of Milaculum. Two new species are described, Milaculum balticum from the Upper Ordovician of Estonia and M. longmyndium from the Lower Silurian of the Welsh Borderland.