Dirtbeds

pl. (Geol.) Dark-colored, loam-like beds, that occur interstratified with the oölitic limestones and sand-stones of Portland, England, and of Nova Scotia. They are evidently the soils in which Fig . 832.-ZAMIA SPIRAL IS. ( South Australia .) plants allied to the Cycads and Zamias of the period grew. Stumps of trees in an erect position, with their roots extending beneath them, have been found in these strata.