GEOL. MAG. 1921. PLATE IL. 
Fic. a.— Channel in Carboniferous Limestone, filled with sandstones and 
shales, the whole overlain by Trias. (Geol. Surv. Photo.) 
Fic, b.—Carboniferous Limestone irregularly eroded, and overlain by sandstones and shales, 
now with a thin later covering of Trias. (Geol. Surv. Photo A 792.) 
