Dimensions: 9 Females- L = .948-1.13 mm; a = 22.4-26.7; b
= 3.58-4.24; c = 9.1-10.2; V = 50-55; Stoma = 22-26u Female- (Holotype): L = 1.03 mm, a = 22.4, b =
3.83, c = 9.6, V = 50u Body slender, tapered little anteriorly, more posteriorly. Cuticle
thick, marked by deep, distinct transverse striae. Striae interrupted
on each side of body by longitudinal alae. Each wing area composed
of a single longitudinal ala, flattened on top and with only the slightest
hint of a central depression. Lip region rounded about half as high
as width. Six lips bluntly conoid, each distinct at base. At
oral opening each lip extends to a short point. Lip region set off
by deep constriction. Four well-developed cephalic setae 4.5 microns
(4-5 microns) long, located two to three annules posterior to lip region.
Stoma length 26 microns (22-26 microns) slightly more than twice width
of lip region. Cheilostom well developed, plates distinct.
Prostom one-third length of meso-metastom. Amphids 18.5 microns (16-19
microns) from anterior extremity located at level of meso-metastrom.
Amphid diameter 3 microns (3-3.3 microns) one-fifth width of neck at their
level. Esophagus approximately one-fourth of total body length.
Excretory pore located at 56.5% (54-58%) of esophagus length. Nerve
ring just anterior to excretory pore. Cervical papillae setiform,
situated outside and dorsal to longitudinal alae, just posterior to excretory
pore. Length of esophago-intestinal valve slightly more than one-third
body width at its level. Vulva usually equatorially located, 50%
(50-55%) of total body length. Vagina extends slightly less than
one-half body diameter into body at vulva. Rectum 27.5 microns (25.5-33
microns). Tail 4.7 (3-5 anal body diameters. Cuticularized
orifice of caudal glands (spinneret) 3.5 microns (3.3-4 microns).
Male: Not known.
Holotype: Female collected August 19, 1957 by A.R. Maggenti,
catalogue no 120, University of California Nematode Survey Collection.
Paratypes: Twelve females same data as Holotype.
Type Habitat: Moss, Oregon Ash (Fraxinus oregona).
Type locality: South fork of Tuolumne River, Lumsden Bridge,
United States Forest Service Camp Grounds, Stanislaus National Forest,
Tuolumne County, California, U.S.A.
Plectus annulatus differs from all other known species of Plectus
by the well-developed cheilostom, the one longitudinal ala on each side
of the body, and the placement of the cervical papillae dorsal to the longitudinal
(Description- Maggenti, 1961)