Material of the Middle Miocene kieselgur deposit of Beuern (Germany, Vogelsberg), about 15 million years old limnic sediment of a volcanic crater lake was investigated with the scanning electron microscope without any previous preparations. The samples mainly consisted of diatom shells and sponge spiculae, but also contained well-preserved tests of euglyphid thecamoebians where, for the first time, individual test scales could be clearly seen. Two species, each represented by several specimens, were investigated in detail. Both had highly characteristic body and aperture scales, which were indistinguishable from those of extant Euglypha crenulata Wailes, 1912 and E. scutigera Penard, 1911. Thus, the fossil specimens were assigned to these extant species which, however, were referred to a new genus, Scutiglypha, characterised by scutiform, crenate body scales. Clearly, details of the scales remained stable over millions of generations, although testate amoebae are largely asexual. The mechanism responsible for this stability is unknown, but intrinsic (“internal”) selection might override environmental (“external”) selection, thus promoting evolutionary stability of main parts of the system.