Page:The Habitat of the Eurypterida.djvu/179

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).

Upper Old Red Sandstone:
2.	Higher subdivision, or Elgin beds (now known to be Triassic).
1.	Lower subdivisions, or Nairn beds. (Extensive unconformity).	0–1,000'

Orcadian Old Red:
5.	John o'Groats Flags.
4.	Thurso or Rousay Beds.
3.	Achanarras, Stromness, and Cromarty Beds.
2.	Berriedale sandstones.
1.	Badbea Breccias and Basal Conglomerate.	0–16,000'

Caledonian Old Red Sandstone:
3.	Strathmore sandstones (the upper part of which may be contemporaneous with the lowest part of the Orcadian).
2.	$\left\{{\begin{aligned}\\\\\\\\\\\\\end{aligned}}\right.$	Myriopod Beds.
		Volcanic Rocks.
		Acanthodian Beds of Turin Hill.
		Cephalaspis Beds of Auchtertyre.
		Volcanic Rocks.
		Pterygotus Beds of Carmylie, etc.
		Tealing Beds.
1.	Lower Series of sandstones, mudstones, conglomerates, etc., base not seen. Ranging to ?			20,000'

(Extensive unconformity).