An order of nematodes in which the taxa are readily recognized by their conspicuous body annulation. The annuli may be covered with concretion rings, or the cuticle may be ornamented with scales, warts, or bristles. The cephalic sensilla reportedly are reduced in number. The internal whorl is absent, the second whorl is papilliform, and the four sensilla of the third circlet are setiform. The vesiculate amphids are oval to circular and occupy much of the cephalic region. The somatic setae are tubular, and the open distal ends are often elaborate. The posterior esophagus is only slightly expanded. When pigment spots or ocelli are present, they are just posterior to the esophagus. Females are amphidelphic, and the ovaries are generally outstretched. The male spicules are generally accompanied by a gubernaculum. Both sexes have three caudal glands.