We studied a variety of chthoniid pseudoscorpions collected from the semiarid zone of Western Australia. Five new species of Tyrannochthonius Chamberlin, 1929 and three new species of Lagynochthonius Beier, 1951 are named and described from the Pilbara and Gasgoyne regions, and surrounding areas such as Barrow Island. Tyrannochthonius basme, sp. nov. and Lagynochthonius asema, sp. nov. from pisolitic mesas near Pannawonica, T. garthhumphreysi, sp. nov. from limestone karst on Barrow Island, T. souchomalus, sp. nov. from calcrete deposits near Cue, T. billhumphreysi, sp. nov. and L. polydentatus, sp. nov. from a calcrete deposit on Sturt Meadows Station and L. leemouldi, sp. nov. from calcrete near Marble Bar are all considered to represent hypogean species as all exhibit typical troglomorphic adaptations including total loss of eyes and attenuated appendages. New records are provided for T. brooksi Harvey and T. butleri Harvey from Cape Range peninsula. A new epigean species, T. aridus, sp. nov., was found on Barrow Island and the Pilbara mainland. Two further putative new species based upon nymphal specimens from subterranean environments are described but not named owing to the lack of adult specimens. Although the epigean species T. aridus, sp. nov. is relatively widespread, all of the subterranean species are thought to represent short-range endemic species as they have been found at very few locations, all of which occur in localised habitats such as limestone or within mesa formations. Tyrannochthonius chamorro Chamberlin, 1947 from Guam is transferred to the genus Lagynochthonius, creating the new combination Lagynochthonius chamorro (Chamberlin 1947).