Page:The Habitat of the Eurypterida.djvu/179

Rh the Upper are the Dura Den beds, which for the most part rest unconformably upon the Lower Old Red or transgressively on older rocks (Geikie, 74, 1006).

Dr. Goodchild, who has worked over the Scottish rocks for nearly fifty years, has taken exception to a number of the prevailing ideas about the Old Red and has given a new subdivision. He has returned to a threefold subdivision for these rocks as they occur in Scotland, the divisions corresponding in many respects to those made by Murchison, although he does not use the terms Lower and Middle because they have been employed with such different meanings by various writers that he deems it best to use locality terms. Thus he gives the following subdivisions of the Old Red sandstone in Scotland, the Orcadian succession being based on Traquair's work (272–275) on the ichthyology and on Flett's studies (66) in the Orkneys (80, 600).

(Extensive unconformity).