The numerous generic splits in Cetraria have long been problematic; a recent paper by Divakar et al. fixes those problems and simplifies the classification. Most cetrarioid lichens are assigned to either Nephromopsis or Cetraria. The following names (among others) are reduced to synonymy: Ahtiana, Allocetraria, Flavocetraria, Kaernefeltia, Masonhalea, Tuckermanella, Tuckermannopsis, and Vulpicida. Gowardia is reunited with Alectoria.
Note, you can download a spreadsheet or pdf that lists the changes relevant to PNW lichens. Click on "Resources", then "Recent literature...", then scroll down to Divakar et al. (2017).
Here is the reference for the paper:
Divakar, P. K., A. Crespo, E. Kraichak, S. D. Leavitt, G. Singh, I. Schmitt, & H. T. Lumbsch. 2017. Using a temporal phylogenetic method to harmonize family and genus-level classification in the largest clade of lichen-forming fungi. Fungal Diversity 84:101. DOI 10.1007/s13225-017-0379-z