• Lips usually fused..
• Large cylindrical buccal cavity, usually with 3 immovable teeth of unequal size  surounded in the posterior region by esophageal tissue
• Esophageal glamds open through the teeth.
• Amphidial fovea pocket-shaped, posterior to buccal cavity.
• Esophagus muscular throughout length, esophageal gland openings just posterior to buccal cavity.
• Males mainly diorchic, spicules varied in shape and size; gubernavulum present or absent.
• Females didelphic amphidelphiuc or monodelphic prodelphic; ovaries reflexed.

Specific characteristsics of the subfamily Octonchinae

•  Buccal cavity sclerotized, tapering posteriorly, with only posterior end surrounded by pharyngeal tissue.
• Buccal armature composed of three typical oncholaimid teeth with one of the ventrosublateral teeth the largest and many additional small teeth either distributed on the wall of buccal cavity or on mandibular ridges.
• Demanian system present or absent, complex when present.
• Females didelphic amphidelphic, ovaries reflexed
• Diorchic, testes opposed, both on right side of intestine.
• Tail conical or conical-cylindrical.
• Marine.

Ref: Shi and Xu, 2016

The Demanian system is a set of canals, junctions and pores unique for some genera of Oncholaimidae. The system differs from simple (primitive) to more complex (advanced) in different genera and species.  The Demanian system  features in "traumatic insemination" in which the male uses spicules and secretions to puncture the cuticle of the posterior of the female to form a copulatory pore. Sperm are released into the pore. The sperm injected into the female move through terminal ducts and reach the main duct of the Demanian system. The sperm move forward in the main duct to the uterus through the uvette and ductus uterinus. Eggs are fetrilized in the uterus ( Coomans et al., 1988; Tchesunov, 2015).