Body slightly arcuate, cylindroid, tapering gradually at extremities.  Lip region very angular, set off by expansion, with prominent papillae. Spear 15 um long with aperture occupying 1/3 its length.  About 2/5 of esophagus enlarged by rather abrupt expansion.  Cardia discoid, then conoid or spheroid.  Intestine thin-walled with scattered dark brown refractive granules.  Vulva transverse with slightly sclerotized labia.  Vagina spheroid, only about 1/3 as long as body width.  Ovaries reflexed about halfway to vulva.  Eggs 30 x 70 um.  Prerectum 2 to 3 times as long as body width.  Rectum about equal to anal body diameter.  Males not found.
    Eudorylaimus aquilonarius is distinctive because of its angular, expanded lip region, posteriorly located vulva, form of vulva labia, spheroid vagina and arcuate tail with small rounded terminus.
    Habitat: Grain field near Fargo, North Dakota, and soil about roots of juniper in windbreak near Forestburg, South Dakota.