Mylestoma bipartitum is described by Kahl as a brackish water or saltwater form. I found Mylestoma bipartitum in a fire-fighting pond on the island Hiddensee. The fire-fighting pond is located near the Hiddensee Biological Station in a south-easterly direction and contains fresh water. Kahl describes Mylestoma bipartitum as euryhaline, which means that the species is very tolerant of salinity. This would explain the finding in fresh water.

Like all species of the genus Mylestoma, the posterior and ventral spines are greatly reduced. I was only able to examine one specimen from the left side, on which there is a bundle of very long cirri at the posterior end (s. fig. 1 a-b). I was able to recognize the two flattened and curved ventral spines mentioned by Kahl (s. fig. 1 a). On the ventral side, in addition to the perizonal ciliary band, there are also 3 short cirri, which originate approximately at the level of the adoral zone (s. fig. 2 a). At the posterior end there are only two inconspicuous spines, which could also be recognized when focusing to the right side ( s. figs. 2 b and 2 c). A macronucleus is present. I could not identify the micronucleus perfectly, but it is possibly separated from the macronucleus (s. fig. 2 b).