Plagiopyla Stein, 1860 (ref. ID; 2013) or 1960 misspelling? (ref. ID; 3690)
Class Kinetofragminophora: Subclass Vestibulifera: Order Trichostomatida (ref. ID; 2013)

[ref. ID; 2013]
Body laterally compressed oval in outline with distinct notch in right hand edge (ventral) in anterior body quarter. Distinct vestibular area in form of a transversely arranged deep ciliated furrow which meets the notch on the right (ventral) edge. The furrow travels approximately halfway across the body on the apparent ventral (left) surface. On the apparent dorsal (right) surface there is a channel-like transversely striated structure which extends initially up from the vestibulum for a short distance before sharply bending down to travel posteriorly along the right edge. There are many ciliary meridians which originate from the vestibular furrow. Body entirely ciliated. Large terminal contractile vacuole. Macronucleus spherical or ovoid, centrally placed. Sapropelic.
Quote; Colin R. Curds "British and other freshwater ciliated protozoa Part I Ciliophora: Kinetofragminophora" Cambridge University Press, 1982 (ref. ID; 2013)

Plagiopyla minuta Powers, 1933 (ref. ID; 4125, 4397)
Description; Endocommensal ciliate of sea urchins. (ref. ID; 4125)
[Somatic Cortex: Kinetids]: The kinetids and alveolar system of this genus are identical to those of Lechriopyla except that the kinetodesmal fibrils do not seem to overlap as extensively, perhaps due to the lesser number of kinetids in a kinety. A parasomal sac is located just anterior to the kinetosome. (ref. ID; 4125)
[Somatic Cortex: Extrusomes]: The extrusomes are distributed between kinetids of the kinety as in Lechriopyla. Very rarely, an extrusome was fixed after extrusion. The extruded organelle appeared to be encased in a thin, dense tube-like sheath which encloses a periodically striated matrix. (ref. ID; 4125)
[Oral Cortex: Striated band]: The striated band of Plagiopyla minuta Powers, 1933 is composed of a series of small, thin cortical ridges that are transversely oriented with respect to the longitudinal axis of the band. These ridges are ~ 2 um high, ~0.2 um wide, and separated by ~0.4 um. In the narrowest portion of the ridges, the epiplasmic layer becomes almost contiguous. The lateral edges of the striated band are supported by groups of macrotubules which are organelles similar in structure to microtubules but having a larger diameter that border the inter-ridge space. (ref. ID; 4125)
Plagiopyla minuta Stein (ref. ID; 1618)
Description; In the intestine of Strongylocentrotus droebachiensis. (ref. ID; 1618)
Measurements; 50-75 by 36-46 um. (ref. ID; 1618)
Plagiopyla nasuta Stein, 1860 (ref. ID; 3116, 4488, 4612) reported year? (ref. ID; 1219, 1308, 1335, 1618, 1622, 1629, 2245, 3690) reported author and year? (ref. ID; 191)
Syn; Paramecium cucullio Quenn., 1867 (ref. ID; 3116)
Description; Dorso-ventrally flattened; uniform ciliation, sometimes yellowish or beige in color, oral groove transverse, cytostome on the left end; a so-called "striated structure" is present on the dorsal side starting from the edge of the mouth groove and turning backwards; trichocysts in large numbers all over the body; macronucleus near the right margin in the middle of the body; P. nasuta exhibits great morphological variability. (ref. ID; 1219)
Ovoid; tapering anteriorly; peristome at right angles or slightly oblique to the edge; trichocysts at right angles to body surface; macronucleus round to irregular in shape; sapropelic in brackish water. (ref. ID; 1618)
Measurements; Length 80-180 um. (ref. ID; 1219)
Body about 100 (80-180 um) long. (ref. ID; 1618)