Change based on synonymy in A Cumulative Checklist for the Lichen-forming, Lichenicolous and Allied Fungi of the Continental United States and Canada, Version 21, which in turn is based on Arup et al. (2013). Arup et al. have this to say about the genus Polycauliona:

Polycauliona is large genus consists of the smaller-sized foliose and fruticose species, formerly included in Xanthoria together with crustose as well as placodioid and leprose species. Even within the former Xanthoria candelaria group in a more narrow sense there are closely related species with crustose, placoid (P. stellata) or delicately foliose thallus (P. candelaria). In the ITS analysis there is no support for Polycauliona (PP = 0.4), but in the combined analysis there is full support. Within the genus there are also three fully supported subclades, which could be recognized as genera. One consists of only crustose members and two consist of lobate, crustose and subfruticose or foliose species. Recognizing them at the generic level does not make more sense than keeping them as one genus, the level of information does not increase considerably, and we therefore prefer one large genus with an obvious distribution centre, viz. southwestern North America.

This is actually the type for the new genus. Arup et al. note that the type specimen was from San Francisco. Tuckerman's original description can be found at http://biodiversitylibrary.org/page/3097213