Oh. XXVL] OLD RED SANDSTONE. 523 



ductive coal-measures ; and, although very inconspicuous on the mar- 

 gin of the Alleghany or Great Appalachian coal-field in Pennsylvania, 

 it expands in Virginia and Tennessee. Its still greater extent and 

 importance in the Western or Mississippi coal-fields, in Kentucky, 

 Indiana, Iowa, Missouri, and other "Western States, has been well 

 shown by Dr. D. Dale Owen. In those regions * it is about 400 feet 

 thick, and abounds, as in Europe, in shells of the genera Productus 

 and Spirifer, with Pentremites, and other crinoids and corals. Among 

 the latter, Lithostrotion basaltiforme or striatum (fig. 565, p. 516), or 

 a closely-allied species is common. 



CHAPTER XXVL 



OLD RED SANDSTONE, OR DEVONIAN GROUP. 



Old Red Sandstone of the Borders of Wales— Of Scotland and the South of Ire- 

 land — Fossil Devonian plants at Kilkenny — Holoptychius of the Middle and 

 Cephalaspis of the Lower Old Red of Forfarshire — Pterygotus and supposed 

 eggs of Crustaceans — Northern type of Old Bed in Scotland — Classification of 

 the Ichthyolites of the Old Red, and their relation to living types — Distinct 

 lithological type of Old Red in Devon and Cornwall — Term "Devonian" — Or- 

 ganic remains of intermediate character between those of the Carboniferous and 

 Silurian systems — Devonian series of England and the Continent — Upper Devo- 

 nian rocks and fossils — Middle — Lower — Old Red Sandstone of Russia — Prepon- 

 derance of Brachiopoda — Devonian strata of the United States and Canada — 

 Coral reefs at the falls of the Ohio — Gaspe Sandstone — Vegetation of the Devo- 

 nian period. 



It has been already shown in the section (p. 431), that the car- 

 boniferous strata are surmounted by a system called " The New 

 Red," and underlaid by another termed the " Old Red Sandstone." 

 The last-mentioned group acquired this name because in Hereford- 

 shire 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 de- 

 termined by the red oxide of iron. 



" Old Red " in Herefordshire, &c. — In Herefordshire, Worcester- 

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



* Owen's Geol. Survey of Wisconsin, &c, 1852. 



