Hammerschmidtiella andersoni sp. n.(Thelastomatidae: Oxyurida) is described from the posterior gut of Archispirostreptus tumuliporus (Spirostreptida: Diplopoda) from Saudi Arabia. The new species is distinguished from all previously described species in the genus except for H. manohari by its slender shape and by the fact that the cephalic annules decrease abruptly in size after the first few annules. The 2 species are distinguished by the fact that the anterior, long annules alternate with short annules in H. andersoni but not in H. manohari. The new species further differs from H. manohari in having an unflexed testis, a much shorter tail in the male, and by the form of cytoplasmic processes surrounding the oral opening of the female. Finally, the new species is the only species in the genus in which a gubernaculum has been reported. The karyotype of H. diesingi is shown to be the same as that of//, andersoni, namely 5 in males and 10 in females.