Œsophagus consisting of a chain of single cells, the lumen of the œsophagus passing through their centre. Ovary single. Vulva at junction of anterior and posterior portions. Sub-families: (1) Trichurinæ, (2) Trichinellinæ.
Family. Dioctophymidæ.
Body anteriorly armed with spines or unarmed; mouth without lips, with six, twelve, or eighteen papillæ in one or two circles; œsophagus very long without a bulb; anus terminal in female; one ovary; vagina very long; spicule in male very long; bursa cup-shaped without rays (Dioctophyme, Hystrichis, Eustrongylides).
Family. Strongylidæ, Cobbold, 1864.
Bursa, supported by rays, always present. Oviparous.
Family. Physalopteridæ.
Mouth with two large lips. Bursa with supporting papillæ in form of a lanceolate cuticular expansion, with genus Physaloptera.
Family. Ascaridæ, Cobbold, 1864.
Rather thick Nematodes. Mouth with three lips—one dorsal, two latero-ventral. Sub-families: (1) Ascarinæ, (2) Heterakinæ, etc.
Family. Oxyuridæ.