Body relaxed in an open spiral. Annules becoming much finer near head. Lip region hemispherical with 4 very fine annules, sometimes difficult to resolve. Spear 20u-23u long with massive, straight or slightly cupped knobs, its muscles attached to strong cephalic arches.  Dorsal esophageal gland outlet 6u behind knobs. Cephalids at 4th and 10th annules, usually not visible because heads are twisted from true lateral view. Excretory pore just behind nerve ring with anteriorly adjacent hemizonid. Ovaries unusually long, their uterine tracts with spheroid offset spermathecae filled with sperms. Terminus variable, with short projection to peg-like extensions which usually are dorsally bent. Caudal striae 6-11. One specimen observed with excessively fine terminal striae.

Male less spiral than female, somewhat more tapering to lip region. Spicula 25u long, slightly arcuate.  Gubernaculum with prominent distal, elongate knob. Bursa finely crenate.  Phasmid usually about one body width anterior to anus.

Helicotylenchus exallus is recognized by its bisexuality, fine striae at anterior end, rather short spear, anteriorly located excretory pore, long ovaries, variable terminus, forward-located phasmids and cephalated gubernaculum.
(Description- Thorne and Malek,1968)