Histriculus Corliss, 1960 (ref. ID; 2014)
Class Polyhymenophora: Subclass Spirotricha: Order Hypotrichida: Suborder Sporadotrichina: Family Oxytrichidae (ref. ID; 2014)
Family Oxytrichidae Ehrenberg, 1838; Subfamily Stylonychinae Berger & Foissner, 1997 (ref. ID; 4894 subfamily original paper)

Synonym Histrio Sterki, 1878: invalid because of homonymy (Corliss 1960) (ref. ID; 2857)
Histrio Sterki, 1878 (type species by original designation: Histrio steinii Sterki, 1878, a junior synonym of Histriculus histrio); (?)Parahistriculus Groliere, 1975 (type species by monotypy: Parahistriculus minimus Groliere, 1975). (ref. ID; 4894)

[ref. ID; 2014]
Inflexible, oval, dorso-ventrally flattened body with a large AZM extending up to halfway down the body length. 2 rows of marginal cirri joining posteriorly and sometimes giving rise to caudal cirri. Transverse cirri present. A series of fronto-ventral cirri scattered on the ventral surface, of which the most anterior are large. Macronucleus in two parts each with a micronucleus. Several species have been described.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)

[ref. ID; 2857]
A vilid oxytrichid genus characterized by a stiff body, confluent marginal cirral rows, and the lack of caudal cirri. (ref. ID; 2857)
See Sterkiella

[ref. ID; 4894]
Improved characterization; Undulating membranes in Oxytricha pattern. One right and one left row of marginal cirri, posteriorly confluent. Six dorsal kineties. Caudal cirri absent. Dorsal morphogenesis in Oxytricha pattern. (ref. ID; 4894)
Remarks; Histrio Sterki is a junior homonym replaced by Corliss (1960). Parahistriculus minimus Groliere, 1975 differs in the dorsal pattern (four kineties only), so that the synonymy is questionable. Oxytricha and related genera have a very supple and slender body, open marginal rows, and caudal cirri. (ref. ID; 4894)
Type species (original designation); Paramaecium histrio Muller, 1773 (ref. ID; 4894)

Histriculus muscorum (Kahl, 1932) (ref. ID; 662, 7423, 7751) or (Kahl, 1932) Corliss, 1960 (ref. ID; 2857, 4695)
See; Sterkiella histriomuscorum (ref. ID; 2846, 7423)
Description; This species is an outdated combination, that is, the species was assigned to the wrong genus; now it is Sterkiella histriomuscorum. (ref. ID; 2857)
The body has more or less oval shape, being slightly oblong and dorsoventrally flattened. This ciliate measures 89 x 49 um on average and has two macronuclei with a size of about 19 x 9 um and two spherical micronuclei, each adjacent to a macronucleus. H. muscorum has 7 frontal cirri, one buccal cirrus, 5 ventral cirri, 5 transverse cirri, 3 caudal cirri and a row of marginal cirri (with 62 cirri on average) which surround the ciliate's body, proceeding posteriad from the most anterior part of the AZM by the posterior end of the ciliate and anteriad along the left side of the ciliate. The AZM has about 44 membranelles and there are two kineties, paroral and endoral, each of which is made up of a simple row of kinetosomes. (ref. ID; 4695)
[Paroral formation]: The paroral formation has two parts in this species: PF 1 and PF 2, each composed of a single row of kinetosomes. Each of these parts of the paroral formation has a parallel fibre. These fibres are designated subparoral fibre 1 (SPF 1), which is parallel to PF 1, and subparoral fibre 2 (SPF 2), parallel to PF 2. In the posterior zone of the oral area, near the cytostome, the subparoral fibres apparently make contact with the perimembranellar fibre (PMF) (which accompanies the adoral membranelle area), giving an appearance of continuity between these fibres (Fernandez-Leborans and Martin-Gonzalez 1982). The fibrillar and kinetosomal composition of the paroral formation is Stylonychia mytilus (Muller 1773; Ehrenberg 1830) is similar to that of Histriculus muscorum (Fernandez-Leborans and Martin-Gonzalez 1982). (ref. ID; 4695)
[Morphological variability]: Six of 29 characters analyzed proved to be constant within and among populations. At the alpha = 0.05 significance level the multiple comparison procedure indicates that 7 attributes - number of adoral membranelles, postoral ventral cirri, etc. - are not significantly different between populations. In nearly all of the remaining 16 characters the arithmetic mean is distinctly higher in population 1. Hence, the tests reveal that most of the significant differences are between this population and the other one. For alpha = 0.1, 0.05, and 0.01 the phenograms of the NNSDC method show that population 1 is different from the cluster P2, P3, and P4 in 27%, 22%, and 18% respectively. The UPGMA cluster analysis of the coefficient of racial likeness yields a phenogram similar to that given by the previous method. (ref. ID; 7751)
[Morphogenesis]: The stomatogenesis commences just left of the transverse cirrus III/1 and the proliferation of basal bodies yields a long and narrow oral primordium with subsequently enlarges and differentiates to adoral membranelles in a posteriad direction. The cytopharynx of the proter is reorganized. The origin and the order of the development of the 6 fronto-ventral-transverse primordia of both filial products are presented. About 88% of the specimens analyzed biometrically (n = 52) possess 4 transverse cirri (6% with 5 and 6% with 3). The high dominant set of 17 cirri, of course without marginal and caudal ones, arises within the streaks. The formation of the new marginal and dorsal rows proceeds as in Stylonychia vorax and S. pustulata (Wirnsberger et al. 1985). However, the right marginal primordium of the proter originates from the second anteriormost cirrus. (ref. ID; 7751)
Remarks; Typical highly evolved parakahliellid species (N1), developing four cirri in each of the two rightmost ventral rows five and six, and the posterior N1 anlagen-part develops at the anteriormost cirrus of the second rightmost row five. Row six is the neokinetally developed rightmost ventral row, of which two cirri migrate during division to a position near the distal membranelles. (ref. ID; 7423)
Sampling site; Population 1: 9.6.1978; wodland, Guttal, Glocknerarea, alt. 1900 m, Karnten. Population 2: 23.10.1980. Population 3: 29.7.1981; alpine pasture (0-5 cm), Schlossalm, alt. 1964 m, Bad Hofgastein, Salzburg. Population 4: 3.7.1982 (ref. ID; 7751)
Histriculus similis (Quennerstedt) Corliss, 1960 (ref. ID; 2124) reported author and year? (ref. ID; 191, 3678, 4609, 4721, 7736)
Description; The ulrastructural study of the cortical morphogenesis. (ref. ID; 7736)