a–c. Metauroleptus arabicus (a, b) and Keronopsis dieckmanni (c) after protargol impregnation. a, b – ventral and dorsal view showing main features, such as the four ventral cirral rows (1–4), the transverse and caudal cirri, and the two macronucleus nodules. The arrowhead marks the last kinetid in dorsal kinety 1; c – ventral view showing a main feature of K. dieckmanni, viz., the four macronucleus nodules. The cirral pattern is highly similar to that of M. arabicus, but caudal cirri are absent from K. dieckmanni. AZM – adoral zone of membranelles, BC – buccal cavity, CC – caudal cirri, DK 1–3 – dorsal bristle rows, FV – food vacuoles, LM – left row of marginal cirri, MA – macronucleus nodules, MI – micronucleus, RM – right row of marginal cirri, TC – transverse cirri. Scale bars: 80 μm.