I do not find Chilodontopsis depressa frequently, but regularly. I usually find the specimens in floating plant masses. In the sample containers they collect at the bottom.

At small magnifications, Chilodontopsis appears shoe-shaped and strongly flattened. This can be seen particularly well in freely swimming specimens when they rotate around their longitudinal axis.

At higher magnifications, Chilodontopsis depressa can be recognized as a nassulid ciliate by the oral basket and the so-called synhymenium. The synhymenium, which is also called the hypostomial ciliary band, runs along the ventral side in the front third of the body. It runs underneath the oral basket. In the case of Chilodontopsis depressa, however, the synhymenium does not extend to the dorsal side, as is the case with the genera Nassula or Obertrumia, for example.

At the posterior end, Chilodontopsis depressa has a very large contractile vacuole with a subterminal excretory pore. The contractile vacuole widens considerably on the left side of the body and reaches the level of the oral basket with a canal-like extension. During systole, vacuoles remain, which can be described as auxiliary vacuoles (s. figs. 1 a and 2 a).

Chilodotopsis depressa can be distinguished from the similar species Trithigmostoma cucullus or Zosterodasys transversa by its smaller size and the large, terminal contractile vacuole.

More images and information on Chilodontopsis depressa: Jeffrey Silverman-iNaturalist-Chilodontopsis depressa