Description (from Thorne, 1929)
    Characters of Mononchus muscorum Dujardin.  Pharynx one-fourth deeper with corresponding increase in number of elements in saw-tooth rasp opposite the dorsal tooth.  Amphids much larger and more conspicuous.  Males numerous while M. muscorum is syngonic.  Male tail bears 18 to 20 preanal supplements, three pair of caudal and three pair of preanal submedian papillae.  Spicula one and one fourth-times as long as the anal body diameter, thick and strong with bifurcate lateral guiding pieces and long slender accessory pieces.
    Excessively fine striae are visible on the extremities.  The distinctly expanded lip region bears the usual two circlets of very prominent papillae.  The amphids are a conspicuous feature owing to the inner extensions which are very distinct on some specimens.  The capacious pharynx bears the dorsal tooth near its entrance and this is opposed by a row of denticles on the opposite side, usually about 18 in number.  The esophagus is at first one-half the neck width but after passing through the nerve ring is about three fifths as wide as the neck.  The disc shaped cardia is half as wide as the body.  An indistinct pore is opposite the verve ring, probably the renette pore.  The somewhat tesselated intestine is six to eight cells in circumference.  All the females were too young to show any details of the ovaries.  The rectum is about as long as the anal body-diameter.
    The thick, blunt spicula rest on slender accessory pieces that are connected by muscular bands to the furcate guiding pieces.  Pores lie about one-third the tail length from the terminus.
    Remains of devoured nemas were found in the intestines of several specimens.
    Two males and five immature females in the collection