The Lichen Peltigera britannica
Shown growing on a moss covered rock three steps from our back door. Usually lumped in with P. aphthosa this lichen is differentiated by its peltate cephalodia.
The cephalodia of P. aphthosa are tightly appressed as mentioned in “Macrolichens of the Pacific Northwest, Second Edition”. One of the common names, Flaky Freckled Pelt Lichen, is due to the many secondary photobiont containing cephalodia.
Although published in 1995 this article is a fine reference.
http://www.friendsofkootenay.ca/sites/default/files/Goward et al 1995.pdf