| abstract | The taxonomic placement of Xenillus is reviewed as a basis for the establishment and characterization of the new family, Xenillidae. The family is differentiated from Liacaridae primarily by the rugose or pitted integument, relatively broad, rugose lamellae with or without cusps and mucro, types and numbers of notogastral and ventral setae. The distinctive traits of the type genus and species, X. clypeator, and X. latus, X. tegeocranus, X. splendens, X. sculptrus are summarized and illustrated. Four new species are described and figured, X. gelasinus from Utah, X. anasillus from Lebanon, X. phryxothrixus from North Carolina, and X. ionthadosus from Georgia, Louisiana, Utah, and North Carolina. Stenoxenillus atraktus, n. gen., n. sp., from North Carolina is described and illustrated. Three new species of the new genus Stonyxenillus are described, S. spilotus from North Carolina, S. anakolosus from North Carolina, Tennessee, and Alabama, and S. akidosus from Virginia. Another new genus and species, Leuroxenillus trichionus from Oregon, is also described. A key to the genera and species is included. |