Eighteen described Acarosporaceae are reported from the Chihuahuan Desert in southern New Mexico. Ten species reported by Magnusson from northern New Mexico were collected in the Chihuahuan Desert. Four species described by Magnusson are revised and taken out of synonymy: Acarospora amabilis, A. applanata, A. carnegiei and A. tenebrica. The squamulose yellow species A. organensis, new for science, was determined as A. xanthophana by Magnusson, a species endemic to South America. Acarospora organensis differs in having a higher hymenium than the two common and similar squamulose species, A. socialis from coastal Mexico and California and A. radicata from the New Mexican, Mojave and Sonoran Deserts. Acarospora subcontigua is reported new for North America.