Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Notes: The considerable confusion over names for the common soil species is well discussed by Hale (1990, p. 81), who separates X. camtschadalis (Ach.) Hale as being uniformly white maculate and the predominately South American X. vagans (Nyl.) Hale as having stictic acid instead of salazinic acid. Another name often used is the Southern Hemispheric X. molliuscula (Ach.) Hale, another stictic acid containing species that has a canaliculated lower surface and often has well developed lobules. The even more strongly tubular Australian species, X. convoluta (Krempelh.) Hale also has salazinic acid. lobulae: plane to convex, irregularly branched, 0.05-1 mm wide Note: Earlier reports (Nash 1974b, Hale 1979) usually referred to this species as X. taractica in the Southwest, but the latter species is now treated as a Southern Hemispheric species that is larger, more loosely adnate and typically occurs on soil (Nash et al. 1986). In contrast to the very common X. lineola (Berry) Hale, X. coloradoënsis is lobulate. The lobulae are very loose and do not form a mat found in some other species whereas the main lobes are quite adnate.