Two new species of the cyanobacterial lichen genus Pterygiopsis from southwestern North America are described. Pterygiopsis cava occurs on siliceous rock in central and southeastern Arizona. It is characterized by a dwarf-fruticose thallus with hollow, internally corticate lobes, polysporous asci, and pycnoascocarps. Pterygiopsis mutabilis occurs on volcanic rock in Baja California Sur. It is variable in thallus shape starting with rosulate squamules which eventually develop into densely lobulate cushions. The lobules have a thick, paraplectenchymatous basal layer, the asci are 8-spored and the ascomatal ontogeny starts from a spheroid tangle of generative hyphae. Records of Pterygiopsis atra are given and P. canariensis is reported for the first time from the United States. A key to the species of Pterygiopsis in southwestern North America is provided.