Diagnosis: Body size 0.9-1.3 mm. Cuticle smooth, sub-cuticle
finely annulated. Lip region offset, lateral lips with two thickenings
in outer portion. Odontostyle simple, dorylaimoid. Guiding
ring single. Odontophore rod-like. Oesophagus typical dorylaimoid
type. Vulva a transverse slit, opening into lightly cuticularised
cavity. Female reproductive system amphidelphic. Spicules
dorylaimoid; ventromedian supplements contiguous. Tail short, dorsally
convex, rounded in both sexes.
Type and only species: Crassolabium australe Yeates,
Remarks: Siddiqi (1969) synonymised Crassolabium with Eudorylaimus.
Andrassy (1976) initially considered it valid but in 1986 treated it as
a synonym of Thonus.
(Description- Jirajpuri and Ahmad, 1992)