Placus Cohn, 1866 (ref. ID; 2013, 7521)
Class Kinetofragminophora: Subclass Gymnostomata: Order Prostomatida: Suborder Prorodontina: Family Prorodontidae (ref. ID; 2013)
Kinetofragminophora: Gymnostomata: Prostomatida (ref. ID; 7521)

Synonym Spathidiopis Fabre-Domergue (ref. ID; 1618), Spathidiopsis Fabre-Domergue, 1889 (ref. ID; 3540), Thoracophrya Kahl, 1926 (ref. ID; 1618, 2013, 3540)

[ref. ID; 2013]
Body outline shape oval, small (30-70 um long), slightly compressed. Pellicle with conspicuously spiral ridges with distinct spots in the furrows between the ridges. Oral aperture oval and apically located, cytopharynx supported by trichites. Somatic ciliature uniform, with cilia emerging from spiral meridians of paired kinetosomes. There is a fibril (shown in protargol preparations) on the left of each pair of kinetosomes. The dorsal 'brush' is composed of a double parallel row of kinetosomes which arises adjacent to the oral aperture and terminates almost halfway down the body at the site of a lateral invagination of unknown function. Macronucleus ovoid to elongate, centrally located. Contractile vacuole either posterior or posterio-lateral.
Quote; Colin R. Curds "British and other freshwater ciliated protozoa Part I Ciliophora: Kinetofragminophora" Cambridge University Press, 1982 (ref. ID; 2013)

Placus socialis Fabre-Domergue, 1889 (ref. ID; 1335, 1619, 3540, 7521) reported year? (ref. ID; 1618)
Syn; Nassula microstoma Calkins, 1903(?) (ref. ID; 1619, 3540) or Cohn, 1866 (ref. ID; 1622); Placus striatus Gourret & Roeser, 1886(?) (ref. ID; 1619, 3540); Thoracophrya marina Kahl, 1927 (ref. ID; 1619, 3540)
Description; Salt water. (ref. ID; 1618)
The ultrastructural study. (ref. ID; 7521)
Measurements; 40-50 by 28-32 um, about 22 um thick. (ref. ID; 1618)