Ch. xxvi.1 old red sandstone. 411 



CHAPTER XXVI. 



OLD RED SANDSTONE, OR DEVONIAN GROUP. 



Old Ked Sandstone of the Borders of "Wales — Of Scotland and the South of 

 Ireland — Foseil reptile and foot-tracks at Elgin — Fossil Devonian plants at 

 Kilkenny — Ichthyolites of Clashbinnie — Fossil fish, crustaceans, <fec, of Caith- 

 ness and Forfarshire — Distinct lithological type of Old Red in Devon and 

 Cornwall — Term Devonian— Organic remains of intermediate character be- 

 tween those of the Carboniferous and Silurian systems — Devonian series of 

 England and the Continent — Upper Devonian rocks and fossils — Middle — 

 Lower — Old Red Sandstone of Russia — Devonian strata of the United States — 

 Coral-reefs at the Falls of the Ohio. 



It has been already shown in the section (p. 332), that the carbonifer- 

 ous strata are surmounted by a system called " The New Red," and un- 

 derlaid by another termed the " Old Red Sandstone." The last-mentioned 

 group acquired this name because in Herefordshire and Scotland, where 

 it was originally studied, it consisted chiefly of red sandstone, shale, and 

 conglomerate. It was afterwards termed " Devonian," for reasons which 

 will be explained in the sequel. For many years it was regarded as very 

 barren of organic remains ; and such is undoubtedly its character over 

 very wide areas where calcareous matter is wanting, and where its color 

 is determined by the red oxide of iron. 



" Old Red " in Herefordshire, &c. — In Herefordshire, Worcestershire, 

 Shropshire, and South Wales, this formation attains a great thickness, 

 sometimes between 8,000 and 10,000 feet. In these regions, it has been 

 subdivided into 



1st. Conglomerate, passing downwards into chocolate-red and green 

 sandstone and marl. 



2d. Marl and cornstone, — red and green argillaceous spotted marls, 

 with irregular courses of impure concretionary limestone, provincially 

 called Cornstone, and some beds of white sandstone. In the cornstones, 

 and in those flagstones and marls through which calcareous matter is 

 most diffused, some remains of fishes of the genera Onchus and Cepha- 

 laspis occur. Several specimens of the latter have been traced to the 

 lowest beds of the " Old Red," in May Hill, in Gloucestershire, by Sir 

 R. Murchison and Mr. Strickland.* 



Old Red Sandstone of Scotland and Ireland. — South of the Gram- 

 pians, in Forfarshire, Kincardineshire, and Fife, the Old Red Sandstone 

 may be divided into three groups. 



* Murchison's Siluria, p. 245. 



