[ref. ID; 2013]
Body ovoid with anterior truncated and posterior broadly rounded. The ventral surface is divided by a wide slot which leads to the deep peristomial cavity which opens apically. The cytopharynx is bent towards the animal's left. There is a line of membranelles which winds clockwise around the apex of the cell and plunges into the peristomial funnel on the left. The body is uniformly ciliated. The macronucleus is rounded and there is a single laterally positioned contractile vacuole. The cytoplasm is usually full of green zoochlorellae. Most easily confused with Bursaria which, unlike Thylakidium has a divided peristomial cavity. It could also be mistaken for Bursaridium whose cytopharynx bends to the right to the right not to the left as in Thylakidium.
Quote; Colin R. Curds "British and other freshwater ciliated protozoa Part I Ciliophora: Kinetofragminophora" Cambridge University Press, 1982 (ref. ID; 2013)