CONTENTS. x iij 



prints of reptilians — First land-shell found — Earity of air-breathers, whether 

 vertebrate or invertebrate, in Coal-measures — Mountain limestone — Its corals and 

 marine shells, .....-- page 496 



Chapter XXVI. — Old Red Sandstone, or Devonian Group. 



Old Bed 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 Bed of Forfarshire — Pterygotus and supposed 

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

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

 lithological type of Old Bed 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 Bed Sandstone of Bussia — 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, --------- 523 



Chapter XXVII. — Silurian and Cambrian Groups. 



Silurian strata formerly called Transition — Term "Grauwacke" — Subdivisions of 

 Upper, Middle, and Lower Silurians — Ludlow formation and fossils — Oldest 

 known remains of fossil fish — Wenlock formation, corals, cystideans, trilobites — 

 Middle Silurian or Llandovery Beds — Lower Silurian rocks — Caradoc and Bala 

 Beds — Upper and Lower Llandeilo formations — Cystideae— Trilobites — Grapto- 

 lites — Vast thickness of Lower Silurian strata, sedimentary and volcanic, in 

 Wales — Foreign Silurian equivalents in Europe — Silurian strata of the United 

 States — Amount of specific agreement of fossils with those of Europe — Canadian 

 equivalents — Whether Silurian strata of deep-sea origin — Cambrian rocks — 

 Classification and nomenclature — Barrande's primordial fauna — Upper Cam- 

 brian of Wales — Tremadoc' slates — Lingula flags — Lower Cambrian — Long- 

 mynd group — Oldest organic remains known in Europe — Foreign equivalents of 

 the Cambrian group — Primordial zone of Bohemia — Characteristic trilobites — 

 Metamorphosis of trilobites — Alum schists of Sweden and Norway — Potsdam 

 sandstone of United States and Canada — Footprints near Montreal — Quebec 

 strata and Huronian rocks — ^finnesota trilobites — Bocks older than the Cam- 

 brian — Laurentian group, Upper and Lower — Oldest known fossil, JEozoon Cana- 

 dense — No remains of vertebrate animals known in strata below the Upper 

 Silurian — Progressive discovery of vertebrata in older rocks — Theoretical infer- 

 ences from the rarity or absence of vertebrata in the most ancient fossiliferous 

 formations, --------- 549 



Chapter XXVDJ. — Volcanic Rocks. 



Trap Bocks — Name, whence derived — Their igneous origin at first doubted — Their 

 general appearance and character — Volcanic cones and craters, how formed — 

 Mineral composition and texture of volcanic rocks — Varieties of felspar — 

 Hornblende and augite — Isomorphism — Bocks, how to be studied — Basalt, 

 trachyte, greenstone, porphyry, scoria, amygdaloid, lava, tuff — Agglomerate — 

 Laterite — Alphabetical list, and explanation of names and synonyms, of volcanic 

 rocks — Table of the analyses of minerals most abundant in the volcanic and 

 hypogene rocks, ----._.. 592 



Chapter XXIX. — Volcanic Rocks, continued. 



Trap dikes — sometimes project — sometimes leave fissures vacant by decomposi- 

 tion — Branches and veins of trap — Dikes more crystalline in the centre — 



