aw = cat ITAA EAE Re RE PE MATS manpage npn nto whee Sis PRO ELE RE PEN wernt Pibrary of the Museum OF COMPARATIVE ZOOLOGY, AT HARVARD COLLEGE, CAMBRIDGE, MASS. Founded by private subscription, iu 1861. The gift of ALEX. AGASSIZ. No. hai hs | Mec il hug. LY / 7 ahha Pl i“ i * ee re ih ¥ e ¥ 4 be Bee. 5 if ENP WN aS: , 1 Say, é ut te 4 reed a ny ate = eee Re yt ii 7 4 % 2 ay <— : a Lae 7 ’ ¥ % se ~ »? Fu Le ait aoe, pe j os -% = “¢ ‘ ‘. cane Me 4 oe 7° hy Oa 48. Roe oe) Shee ee we a ste a Pig 7 oes ; | eae > adie) , ov Vt oe, f J ‘ , i ‘ ye ant" an La, Leauiiete- Seno A sink ae : fot oe eA, weet 2 S Aaa ts 4 P 7 } ” ve) oe Page es > uf i-6 ON art 7 a, ~~ fe toy wre Y Oe ly be A eed ¥ THE INGEN LiPeeiaroRy OF ss id ei law 2 ha i WORKS BY THE SAME AUTACE i: A MANUAL OF 200 LOG FOR THE USE OF STUDENTS. WITH A GENERAL INTRODUCTION ON THE PRINCIPLES OF ZOOLOGY. Fourth Edition, revised and enlarged. Crown 8vo, pp. 732, with 300 Engravings on Wood, 12s.. 6d. Il. LEX T= BOOK, OF »ZOGLeUGy, FOR THE USE OF SCHOOLS. Second Edition, enlarged. Crown 8vo, with 188 Engravings, 6s. = ate INTRODUCTORY TEXT-BOOK OF ZOOLOGY, FOR THE USE OF FUNIOR CLASSES. With 127 Engravings. A New Edition, 3s. Iv. OUTLINES OF NATURAL HISTORY, FOR BEGINNERS. BEING DESCRIPTIONS OF A PROGRESSIVE SERIES OF ZOOLOGICAL TYPES. Fcap. 8vo, with Engravings, Is. 6d. V. A MANUAL OF PALAONTOLOGY, FOR THE USE OF STUDENTS. WITH A GENERAL INTRODUCTION ON THE PRINCIPLES OF PALEONTOLOGY. Crown 8vo, with upwards of 400 Engravings, I5s. vi. A MONOGRAPH OF .THE BRITISH GRAPTOLITIDA. Octavo, with Engravings, 5s. VII. INTRODUCTION TO THE STUDY OF BIOLOGe Crown 8vo, with numerous Engravings, 5s. WILLIAM BLACKWOOD & SONS, EDINBURGH AND LONDON. THE ANCIENT, LhrRRsHISTORY OF TEP EFA eee A COMPREHENSIVE, OUTLINE OF THE PRINCIPLES AND LEADING FACTS OF PALAEON- TOLOGICAL SCIENCE BY Pos Le YN NPC Ores Oe M.D., D.Sc., M.A., Pu.D. (GérrT.), F.R.S.E., F.L.S. PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF ST ANDREWS WELLIAM ._BLACK WOOD: AND. SONS EDINBURGH AND LONDON ” MDCCCLX XVII All Rights of Translation and Reproduction reserved ; T i o 2 re ‘ , ‘Ss f ev 4 } - = ; } Bo . / ery Ne sirens : : ; all Male ea aL ’ ‘ . — aah Met aa ake vipat ee KircoRoin Re eH ALOIEE ASS a+ £ os ; ri ey i) Cave - } ‘ heat oa Lomi, ai in Ws ies PRs Ear THE study of Palzontology, or the science which is concerned with the living beings which flourished upon the globe during past periods of its history, may be pursued by two parallel but essentially distinct paths. By the one method of inquiry, we may study the anatomical characters and structure of the innumerable extinct forms of life which lie buried in the rocks simply as so many organisms, with but a slight and secondary reference to the ¢z#me at which they lived. By the other method, fossil animals are regarded prin- cipally as so many landmarks in the ancient records of the world, and are studied “zstorically and as regards their relations to the chronological succession of the strata in which they are entombed. In so doing, it is of course impossible to wholly ignore their structural characters, and their relationships with animals now living upon the earth; but these points are held to occupy a subordinate place, and to require nothing more than a comparatively general attention. In a former work, the Author has endeavoured to furnish a summary of the more important facts of vi PREFACE. Paleontology regarded in its strictly scientific aspect, as a mere department of the great science of Biology. The present work, on the other hand, is an attempt to treat Paleontology more especially from its historical side, and in its more intimate relations with Geology. In accordance with this object, the introductory portion of the work is devoted to a consideration of the general ‘principles of Paleontology, and the bearings of this science upon various geological problems—such as the mode of formation of the sedimentary rocks, the reac- tions of living beings upon the crust of the earth, and the sequence in time of the fossiliferous formations. The second portion of the work deals exclusively with Historical Paleontology, each formation being consid- ered separately, as regards its lithoiogical nature and subdivisions, its relations to other formations, its geo- graphical distribution, its mode of origin, and its char- acteristic life-forms. In the consideration of the characteristic fossils of each successive period, a general account is given of their more important zoological characters and their relations to living forms; but the technical language of Zoology has been avoided, and the aid of illustrations has been freely called into use. It may therefore be hoped that the work may be found to be available for the purposes of both the Geological and the Zoological student ; since it is essentially an outline of Historical Paleontology, and the student of either of the above- mentioned sciences must perforce possess some know- ledge of the last. Whilst primarily intended for stu- dents, it may be added that the method of treatment adopted has been so far untechnical as not to render the work useless to the general reader who may desire PREFACE, vil to acquire some knowledge of a subject of such vast and universal interest. In carrying out the object which he has held before him, the Author can hardly expect, from the nature of the materials with which he has had to deal, that he has kept himself absolutely clear of errors, both of omission and commission. ‘The subject, however, is one to which he has devoted the labour of many years, both in studying the researches of others and in personal investigations of his own; and he can only trust that such errors as may exist will be found to belong chiefly to the former class, and to be neither serious nor numerous. It need only be added that the work is necessarily very limited in its scope, and that the necessity of not assuming a thorough previous acquaint- ance with Natural History in the reader has inexorably restricted its range still further. The Author does not, therefore, profess to have given more than a merely general outline of the subject ; and those who desire to obtain a more minute and detailed knowledge of Paleontology, must have recourse to other and more elaborate treatises. UNITED COLLEGE, ST ANDREWS, October 2, 1876. Fe BI ee aie ae 4h DAMA he Pag hotvias « F SLSR iv ae aw, as ' ‘ e > AVE? 9 at i} 20 eT ee eh Sea ‘se Bis. tee tee iP to og < OR, ee ee i, Brit Sy)..tut aig! 2s Ata wy a atic an isle oy | bey: wine a oe tie Deen ate pte Mis BAG Vea. ah oR fot dioai ei | ; ie 3). RB wre tit pay ¥ * a UC as ae Be se ee et eee eM ER Foch ost th eee. Hub Ovni Wes Sint 4 to) i. 2 eek nT cr. : S23 a ’ ” as 7 @ i "3 re : - ; oa . : P . hs .s \ * : . ‘ c 1 | 7" iy J 2 > . f : i ; . pee agen ama EO NTE Neies: PoAs ke Bias PRINCIPLES OF PALZONTOLOGY. INTRODUCTION. PAGE The general objects of geological science—The older theories of catastrophistic and intermittent action—The more modern doc- trines of continuous and uniform action—Bearing of these doc- trines respectively on the origin of the existing terrestrial order— Elements of truth in Catastrophism—General truth of the doc- trine of Continuity—Geological time, . - : ; I-10 CHAPTER “I. Definition of Palzontology—Nature of Fossils—Different processes of fossilisation, : « . ‘ : . 5 10-14 CHAPTER Tt Aqueous and igneous rocks—General characters of the sedimentary rocks—Mode of formation of the sedimentary rocks—Definition of the term ‘‘ formation ”—Chief divisions of the aqueous rocks —Mechanically-formed rocks, their characters and mode of origin —Chemically and organically formed rocks—Calcareous rocks— Chalk, its microscopic structure and mode of formation—Lime- stone, varieties, structure, and origin—Phosphate of lime—Con- cretions—Sulphate of lime—Silica and siliceous deposits of vari- ous kinds—Greensands—Red clays—Carbon and carbonaceous deposits, . : : : ‘ : : - ; - 14-36 CHAPPER. LET. Chronological succession of the fossiliferous rocks—Tests of age of strata—Value of Palzeontological evidence in stratigraphical Geo- logy—General sequence of the great formations, - ; 37-44 x CONTENTS. CHAPTER IV. The breaks in the paleontological and geological record—Use of the term ‘‘ contemporaneous” as applied to groups of strata— General sequence of strata and of life-forms interfered with by more or less extensive gaps — Unconformability—Phenomena im- plied by this—Causes of the imperfection of the paleontological record, . : . : : : : : - : 44-52 CHAPTER V. Conclusions to be drawn from fossilsK—Age of rocks—Mode of origin of any fossiliferous bed—Fluviatile, lacustrine, and marine de- posits—Conclusions as to climate—Proofs of elevation and subsi- dence of portions of the earth’s crust derived from fossils, . 52-56 CHAPTER JV. The biological relations of fossils—Extinction of life-forms—Geolo- gical range of different species—Persistent types of life—Modern origin of existing animals and plants—Reference of fossil forms to the existing primary divisions of the animal kingdom—Depart- ure of the older types of life from those now in existence—Re- semblance of the fossils of a given formation to those of the for- mation next above and next below—Introduction of new life- forms,” *~. : : : : : : ; : ‘ 57-61 PAR D1. HISTORICAL PALAZZONTOLOGY. CHAPTER VII. The Laurentian and Huronian periods—General nature, divisions, and geographical distribution of the Laurentian deposits— Lower and Upper Laurentian—KReasons for believing that the Lauren- tian rocks are not azoic based upon their containing limestones, beds of oxide of iron, and graphite—The characters, chemical composition, and minute structure of Hozod Canadense—Compar- ison of Zozodn with existing Foraminifera— Archeospherine— Huronian formation—Nature and distribution of Huronian de- posits— Organic remains of the Huronian—Literature, - 65-76 CHAPTER. VI The Cambrian period—General succession of Cambrian deposits in Wales—Lower Cambrian and Upper Cambrian—Cambrian de- posits of the continent of Europe and North America—Life of the Cambrian period — Fucoids— Eophyton—Oldhamia— Sponges— Echinoderms—Annelides— Crustaceans—Structure of Trilobites —Brachiopods—Pteropods, Gasteropods, and Bivalves—Cephalo- pods—Literature, . : : ' ‘ ‘ ; ; 77-90 CONTENTS. xi CHAPTERAIZG The Lower Silurian period—The Silurian rocks generally— Limits of Lower and Upper Silurian—General succession, subdivisions, and characters of the Lower Silurian rocks of Wales—General succes- sion, subdivisions, and characters of the Lower Silurian rocks of the North American continent—Life of the period—Fucoids— Protozoa—Graptolites—Structure of Graptolites—Corals—Gene- ral structure of Corals—Crinoids—Cystideans— General characters of Cystideans—Annelides—Crustaceans— Polyzoa—Brachiopods —Bivalve and Univalve Molluscs—Chambered Cephalopods— General characters of the Cephalopoda—Conodonts, . - 90-114 CHAP TT Ks xX. The Upper Silurian period—General succession of the Upper Silurian deposits of Wales—Upper Silurian deposits of North America— Life of the Upper Silurian— Plants — Protozoa—Graptolites— Corals—Crinoids—General structure of Crinoids—Star-fishes— Annelides—Crustaceans—Eurypterids— Polyzoa—Brachiopods— Structure of Brachiopods— Bivalves and Univalves— Pteropods— Cephalopods—Fishes—Silurian literature, ; . ei) LE5-132 CHAP TER) XI, The Devonian period—Relations between the Old Red Sandstone and the marine Devonian deposits—The Old Red Sandstone of Scotland—The Devonian strata of Devonshire—Sequence and subdivisions of the Devonian deposits of North America—Life of the period—Plants— Protozoa—Corals—Crinoids—Pentremites— Annelides— Crustaceans — Insects— Polyzoa— Brachiopods—Bi- valves — Univalves—Pteropods—Cephalopods— Fishes—General divisions of the Fishes—Palzeontological evidence as to the inde- pendent existence of the Devonian system as a distinct formation —Literature, ; 5 : : ‘ , : F . 132-157 CHAP TER: oir. The Carboniferous period—Relations of Carboniferous rocks to De- vonian — The Carboniferous Limestone or Sub - Carboniferous series—The Millstone-grit and the Coal-measures—Life of the period—Structure and mode of formation of Coal—Plants of the Coal, ; : ; ‘ , : ‘ : : a Sy -170 CHAPTER: XE. Animal life of the Carboniferous period—Protozoa—Corals—Crinoids —Pentremites—Structure of Pentremites—Echinoids— Structure of Echinoidea — Annelides — Crustacea — Insects—Arachnids— Myriapods— Polyzoa—Brachiopods—Bivalves and Univalves— Cephalopods — Fishes — eee ne cae —.Litera- ture, : iy in Pict BRO ESR CONTENTS. CHAPTER XIV. The Permian period—General succession, characters, and mode of formation of the Permian deposits—Life of the period—Plants— Protozoa — Corals — Echinoderms — Annelides — Crustaceans— Polyzoa — Brachiopods — Bivalves — Univalves — Pteropods — Cephalopods—F ishes—Amphibians—Reptiles— Literature, 192-203 CHAPTER. XV; The Triassic period—General characters and subdivisions of the Trias of the Continent of Europe and Britain—Trias of North America —Life of the period—Plants—Echinoderms—Crustaceans—Poly- zoa—Brachiopods — Bivalves— Univalves— Cephalopods—Inter- mixture of Paleozoic with Mesozoic types of Molluscs—Fishes— sy cae We ig ‘ied ah of Birds—Mammals —Literature, . ; » 202-225 CHAPTER XVI. The Jurassic period—General sequence and subdivisions of the Juras- sic deposits in Britain—Jurassic rocks of North America—Life of the period—Plants—Corals—Echinoderms—Crustaceans— In- sects— Brachiopods— Bivalves— Univalves— Pteropods— Tetra- branchiate Cephalopods—Dibranchiate: Ape ee Reptiles—Birds—Mammals—Literature, . : . 226-256 CHAPTER XVII. The Cretaceous period—General succession and subdivisions of the Cretaceous rocks in Britain—Cretaceous rocks of North America —Life of the period—Plants—Protozoa—Corals—Echinoderms —Crustaceans— Polyzoa — Brachiopods— Bivalves— Univalves— Tetrabranchiate and Dibranchiate CePBB RP eRitg nto tinea lp tiles—Birds—Literature, . : - 256-284 CHAP Tike VT. The Eocene period—Relations between the Kainozoic and Mesozoic rocks in Europe and in North America—Classification of the Tertiary deposits—The sequence and subdivisions of the Eocene rocks of Britain and France—Eocene strata of the United States —Life of the period—Plants—Foraminifera—Corals—Echino- derms— Mollusca—Fishes—Reptiles—Birds—Mammals, . 284-305 CEA PALER ~ ATX. The Miocene period—Miocene strata of Britain—Of France—Of Belgium—Of Austria— Of Switzerland—Of Germany—Of Greece — Of India—Of North America—Of the Arctic regions—Life of the period—Vegetation of the Miocene period — Foraminifera— Corals —Echinoderms—Articulates— Mollusca— aan bians—Keptiles—Mammals, : ; : ‘ » 305-323 CONTENTS. Xill CHAPTER. 22 The Pliocene period—Pliocene deposits of Britain—Of Europe—Of North America—Life of the period—Climate of the period as indicated by the Invertebrate animals—The Pliocene Mammalia —Literature relating to the Tertiary deposits and their fossils, 323-333 CHAPTERGOOS: The Post-Pliocene period—Division of the Quaternary deposits into Post-Pliocene and Recent—Kelations of the Post-Pliocene de- posits of the northern hemisphere to the ‘‘ Glacial period ”— Pre-Glacial deposits—Glacial deposits—Arctic Mollusca in Gla- cial beds—Post-Glacial deposits—Nature and mode of formation of high-level and low-level gravels—Nature and mode of forma- tion of cavern-deposits—Kent’s Cavern—Post-Pliocene deposits of the southern hemisphere, : : : : : - 334-344 GHAPTER, XE Life of the Post-Pliocene period—Effect of the coming on and de- parture of the Glacial period upon the animals inhabiting the northern hemisphere—Birds of the Post-Pliocene—Mammalia of the Post-Pliocene— Climate of the Post-Glacial period as deduced from the Post-Glacial Mammals—Occurrence cf the bones and implements of Man in Post-Pliocene deposits in association with the remains of extinct Mammalia—Literature relating to the Post- Pliocene period, : : : : : : : - 344-366 CHAPTER. CXILL The succession of life upon the globe—Gradual and successive intro- duction of life-forms—What is meant by ‘‘ lower” and ‘‘ higher” groups of animals and plants—Succession in time of the great groups of animals in the main corresponding with their zoological order—Identical phenomena in the vegetable kingdom— Persist- ent types of life—High organisation of many early forms—Bear- ings of Palzeontology on the general doctrine of Evolution, 367-374 APPENDIX.—Tabular view of the chief Divisions of the Animal Kingdom, : ° : ° : : : : Re ye yo. GEOSSARY, . : : : ; s : ‘ : » 379-395 INDEX, . : : : : i : ‘ ‘ ; » 3096-407 G3 ae II. 12: ied 14. rs. 16. ry; XiV LIST OF¢¢LEUSARATIONS: Cast of 7rigonia longa, Microscopic section of the wood of a fossil Conifer, Microscopic section of the wood of the Larch, Section of Carboniferous strata, Kinghorn, Fife, Diagram illustrating the formation of stratified deposits, . 4 Microscopic section of a calcareous breccia, Microscopic. section of White Chalk, . : Organisms in Atlantic Ooze, : : Crinoidal marble, Piece of Nummulitic lime- stone, Pyramids, 3 Microscopic section of Fo- raminiferal limestone— Carboniferous, Amer- ica, : : : Microscopic section of Lower Silurian lime- stone, ; - : Microscopic section of oolitic limestone, Ju- rassic, : ° Microscopic section of ooolitic limestone, Car- boniferous, : Organisms in Barvadees earth, : Organisms in Richmond earth, 4 Ideal section of the erast of the earth, 2 ‘ 27 27 | FIG. 31. . Microscopic . Microscopic Unconformable junction of Chalk and Eocene rocks, Erect trunk of a Sigillaria, Diagrammatic section of the Laurentian rocks, section of Laurentian limestone, . Fragment of a mass of LEozoon Canadense, . Diagram illustrating the structure of Hozoon, . section of Eozoon Canadense, . Nonionina and Gromia, . Group of shells of living Foraminifera, . Diagrammatic section of Cambrian strata, Eophyton Linneanum, Oldhamia antigua, . Scolithus Canadensis, Group of Cambrian Tiilo- bites, . Group of characteristic Cambrian fossils, Fragment of Dictyonema sociale, F ‘ Generalised section of the Lower Silurian rocks of Wales, . ; . Generalised section of fhe Lower Silurian rocks of North America, Licrophycus Ottawaensis, Astylospongia premorsa, . . Stromatopora rugosa, PAGE Dichograptus octobrachiatus , 101 LIST (GF . Didymograptus divarica- tus, ; Diplograptus pristis, . Phyllograptus ty pus, . Zaphrentis Stokest, . . Strombodes pentagonus, . Columnaria alveolata, . Group of Cystideans, . Group of Lower Silurian Crustaceans, . Ptilodictya falciformis, . Ptilodictya Schaffert, . Group of Lower Silurian Brachiopods, . Group of Lower Silurian Brachiopods, . Murchisonia gracilis, . Bellerophon argo, . Maclurea crenulata, . Orthoceras crebriseptum, . Restoration of Orthoceras, . Generalised section of the Upper Silurian rocks, . Monograptus priodon, . LHalysites catenularia and fT, agglomerata, . . Group of Upper Silurian Star-fishes, . Protaster Sedgwickit, . Group of Upper Silurian Crinoids, . Llanolites vulgaris, . : . Group of Upper Silurian Trilobites, . Pterygotus Anglicus, . Group of Upper Silurian Polyzoa, . Spirifera hysterica, : - Group of Upper Silurian Brachiopods, . Group of Upper Silurian Brachiopods, . Pentamerus Knightit, . Cardiola interrupta, C. fibrosa, and FPterinea subfalcata, . . Group of Upper Silurian Univalves, . TZentaculites or natus, . Pleraspis Banksit, . Onchus tenuistriatus and Thelodus, : @encrkaed section of fee Devonian rocks’ of North America, . Psilophyton princeps, | ILLUSTRATIONS. 115. IG: 197. . Generalised . Prototaxites Logant, Stromatopora tuberculata, . Cystiphyllum vesiculosum, . Zaphrentis cornicula, . Heliophyllum exiguum, . Crepidophyllum Archiaci, . Favosites Gothlandica, . Favosites hemispherica, . Spirorbis omphalodes and S. Arkonensis, . Spirorbis laxus and s spinultfera, . Group of Devonian Tri- lobites, . Wing of Platephemera antigua, . Clathropora inter texta, : . Ceriopora Hamuiltonensis, . Fenestella magnifica, . Retepora Phillipst, . Fenestella cribrosa, . Spirifera sculptilis, . Spirifera mucronata, . Atrypa reticularts, . Strophomena rhonbotd- alis, . Platyceras dumosum, . Conularia ornata, . Clymenia Sedgz vickit, - Group of Fishes from the Devonian rocks of North America, . Cephalaspis Lyellit, . Pterichthys cornutus, . Polypterus and Osteolepis, . LHoloptychius nobilisst- mus, . ; Y : section of the Carboniferous rocks of the North of Eng- land, : Odontopteri as Schlotheimii, . Calamites canneformis, . Lepidodendron Sternbersii, . Szgillaria Greseri, . Stiemaria ficoides, . Trigonocarpum ovatum, 114. Microscopic section of Foraminiferallimestone —Carboniferous, North America, Fusulina cylindrica, Group of Carboniferous Corals, Platycrinus tricontadac- tylus, . ‘ : : 161 164 165 167 168 © 169 170 172 174 Xvi “378, 119. 120. 121. 122, 123. 124. 125. 126: 127. 128. 129. 13 131. 132. rea. 34- 35. 36. 137. 138. 139. 140. I4I. 142. 143. 144. 145. 146. 147. 148. 149. 150. 151; 152. 153. 154. 155: 156. LIST. OF Pentremites pyriformis and P. conoideus, Archeocidaris ellipticus, Spirorbts Carbonarius, . Prestwichia rotundata, Group of Carboniferous Crustaceans, : Cyclophthalmus senior, Aylobius Sigillaria, flaplophlebium Barnest, Group of Carboniferous Polyzoa, Group of Carboniferous Brachiopoda, : ; Pupa vetusta, : Gontatites Joss, . Amblypterus macropterus, Cochliodus contortus, Anthracosaurus Russelli, Generalised section of the Permian rocks, . Walchia pintformis, Group of Permian Bra- chiopods, . : ; Arca antiqua, : : Platysomus gibbosus, Protorosaurus Spenert, Generalised section of the Triassic rocks, Zamia spiralis, . Triassic Conifers Cyeadss.) 3 : ; Encrinus lilitformis, . Aspidura loricata, Group of Triassic Bi- valves, Ceratites nodosus, - ; Tooth of Ceratodus ser- vatus and C. altus, Ceratodus Foster, ; Footprints of Cheiro- therium, . Section of tooth of ‘Laby- rinthodont, : Skull of Mastodonsaurus, Skull of Rhynchosaurus, Belodon, Nothosaurus, Paleosaurus, &c., Placodus gigas, Skulls of ‘Dicynodon and Oudenodon, Supposed footprint of Bird, from the Trias of Connecticut, Lower jaw of ’Droma- therium sylvestre, and ILLUSTRATIONS. | 157. Molar tooth of JMcro- 176 | lestes antiquus, 177 | 158. ALyrmecobius fasciatus, 178 | 159. Generalised section of 179 the Jurassic rocks, 160. Alantellia megalophylla, 180 | 161. Zhecosmilia annularis, 18: | 162. Pentacrinus fasciculosus, 182 | 163. Hemicidaris crenularis, . 182 | 164. Lryon arctiformis, 165. Group of Jurassic Bra- 183 chiopods, . ; 166. Ostrea Marshit, 185 | 167. Gryphea incurva, . 186 | 168. Diceras arietina, . 187 | 169. Nerinea Goodhallii, 188 | 170. Ammonites Humphresi- 189 anus, 190 | 171. Ammonites bifrons, 172. Leloteuthis subcostata, 195 | 173. Belemnite restored ; dia- 196 gram of Belemnite ; Belemnites canaliculata, 198 | 174. Zetragonolepis, 3 199 | 175. Acrodus nobilis, 199 | 176. Lcehthyosaurus communis, 201 | 177. Plestosaurus dolichodeirus, 178. Pterodactylus crasstros- 206 UHISS. 208 | 179. Ramphorh ynchus Buck- landt, restored, 209 | 180. Skull of Megalosaur US, . : 210 | 181. Archaeopteryx macrura, . 210 | 182. Archaeopteryx, restored, | 183. Jaw of Amphitherium DAT Prevostit, 212 | 184. Jaws of Oolitic Mam- mals, 214 | 185. Generalised "section of 215 the Cretaceous rocks, . 186. Cretaceous Angiosperms, 216 | 187. Rotalia Boueana, : 188. Siphonia ficus, 217 | 189. Ventriculites simplex, 217 | 190. Synhelia Sharpeana, 218 | 191. Galerites albogalerus, | 192. Discoitdea cylindrica, . 219 | 193. Lscharina Oceani, ° 220 | 194. TZerebratella Astieriana, . 195. Crania [gnabergensts, 221 |. 196. Ostrea Coulont, 197. Spondylus spinosus, 198. Znoceramus sulcatus, 222 | 199. Hippurites Toucasiana, 200. Voluta elongata, . 223 | 201. Nautilus Danicus, : . Forms LIST: OF . Ancyloceras Matheroni- anus, Turrilites catenatus, of Cretaceous Ammonitide, . Belemnitella mucronata, . Tooth of Hybodus, Fin-spine of ybodus, | Ber ‘yx Lewwestensis and Osmeroides Mantellz, . Teeth of Zeuanodon, . Skull of Mosasaurus Canipert, . Chelone Benstedi, : . Jaws and vertebre of Odontornithes, . Fruit of Mipadites, . Nummutlina levigata, . Lurbinoha sulcata, . Cardita planicosta, . Lyphis tubtfer, Cyprea elegans, Cerithium hexagonum, : _ Limnea py camidalis, . Physa columnarts, . Cyclostoma Arnoudii, 3. Rhombus minimus, . Otodus obliquis, » Myliobatis Edwardsit, . Upper jaw of Alligator, . Skull of ee. Lg toliapicus, . Zeuglodon cetoides, . Paleotherium magnum, restored, . Feet of Equide, . Anoplotherium commune, . Skull of Dinoceras mir- abilis, : Vespen tilio Pari. tstensts, . Miocene Palms, . Platanus aceroides, . Cinnamomum Bee phum, . Textularia Meyeri iana, 2 . Scutella subrotunda, ILLUSTRATIONS: | 239. Hyalea Orbignyana, 273 | 240. Tooth of Oxyrhina, 274 | 241. Tooth of Carcharodon, | 242. Andrias Scheuchzert, 274 243. Skull of Lvontotherium 275 | gens, 275 | 244. it ippopotamus Sivalensis, 275 | 245. Skull of Sivatherium, 246. Skull of Deinotherium, 276 | 247. Tooth of Zlephas plant- 278 trons and of Mastodon Sivalensis, . 279 | 248. Jaw of Pliopithecus, 280 249. Rhinoceros Etruscus and R. megarhinus, . 282 250. Molar tooth of Mastodon 290 Arvernensis, 291 | 251. Molar tooth of Elephas 292 | meridionalts, 293 | 252. Molar tooth of Elephas 293 antiquus, . 293 | 253- Skull and tooth of Ma- 204, | chairodus cultridens, 294 | 254. Lecten /slandicus, 294 | 255. Diagram of high- level 294 and low-level gr ravels, 295 | 256. Diagrammatic section of 296 eae. z 296 | 257. Dinornis elephantopus, : 297 | 258. Skull of Diprotodon, 259. Skull of 7hylacoleo, 298 260. Skeleton of Afegatherium, 299 261. Skeleton of AZ;/odon, 262. Glyptodon clavipes, : 301 263. Skull of Rhinoceros ticho- 302 rhinus, ; 303 | 264. Skeleton of Cervus mega CeYOS, : 304 | 265. Skull of Bos primigenius, 305 | 266. Skeleton of Mammoth, 309 | 267. Molar tooth of Mam- 309 moth, 268. Skull of Ursus 1s spelaus, 309 | 269. Skull of Hyena spelea, 311 | 270. Lower jaw of Zrogon- 312 therium. 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( tA ph oe Me ba ie x . tw a P j Ah Lk vhyi # by miesee sah es one ’ Ji Aieetie' ais yeh eo \ ol @ itn) 1A ner ie pret on oe the f We tune wie Ve oa 4% SRE ga ae Ph Wawok at st ean A | 2 hig rae HO) roc» Lele r by; oy | Nib e ‘ ui — r i it ant ‘ 7" eee : Loar om ar ag Pe bal) ; Pi AN, Rip ee ay e ali el By TOP Se. od ARS “Oe Wn ee Ae a ie a. ( be a K i.) pheFat i A LSAae we Sali iit Tome "4 ys in te tay). i. Lailte ag Y DAL eS uz ; ; \% POU Gis be ty haleted. stig Jie i Le & ae Mh ai Pe ISIE GORI. 7. FREE Aire dee pris! |. ecoeplal aya ef ee fi APT ru a's ts wee me pares seth HF He Pity be beh -*\ (eevee ts Vi Pa ae | ’ tig , Are mt eg «ia Ee ivcdee: Weel BRINCIPLES ~OF PALAION TOLOGY. THE PoC Te NY RIP See PO RY OF AES eo BA REE INTRODUCTION: THe Laws OF GEOLOGICAL ACTION. Unpber the general title of “‘ Geology ” are usually included at least two distinct branches of inquiry, allied to one another in the closest manner, and yet so distinct as to be largely capable of separate study. Geo/ogy,* in its strict sense, is the science which is concerned with the investigation of the materials which compose the earth, the methods in which those materials have been arranged, and the causes and modes of origin of these arrangements. In this limited aspect, Geology is nothing more than the Physical Geography of the past, just as Physical Geo- graphy is the Geology of to-day ; and though it has to call in the aid of Physics, Astronomy, Mineralogy, Chemistry, and other allies more remote, it is in itself a perfectly distinct and individual study. One has, however, only to cross the thresh- old of Geology to discover that the field and scope of the science cannot be thus rigidly limited to purely physical pro- blems. The study of the physical development of the earth throughout past ages brings us at once in contact with the forms of animal and vegetable life which peopled its surface in bygone epochs, and it is found impossible adequately to com- * Gr. gé, the earth ; Jogos, a discourse. A 2 PRINCIPLES OF PALZZAONTOLOGY. prehend the former, unless we possess some knowledge of the latter. However great its physical advances may be, Geology remains imperfect till it is wedded with Palzeontology,* a study which essentially belongs to the vast complex of the Biologi- cal Sciences, but at the same time has its strictly geological side. Dealing, as it does, wholly with the consideration of such living beings as do not belong exclusively to the present order of things, Paleontology is, in reality, a branch of Natu- ral History, and may be regarded as substantially the Zoology and Botany of the past. It is the ancient life-history of the earth, as revealed to us by the labours of palzontologists, with which we have mainly to do here; but before entering upon this, there are some general questions, affecting Geology and Paleontology alike, which may be very briefly discussed. ‘The working geologist, dealing in the main with purely phy- sical problems, has for his object to determine the material structure of the earth, and to investigate, as far as may be, the long chain of causes of which that structure is the ultimate re- sult. No wider or more extended field of inquiry could be found ; but philosophical geology is not content with this. At all the confines of his science, the transcendental geologist finds himself confronted with some of the most stupendous problems which have ever engaged the restless intellect of humanity. The origin and primeval constitution of the terres- trial globe, the laws of geologic action through long ages of vicissitude and development, the origin of life, the nature and source of the myriad complexities of living beings, the advent of man, possibly even the future history of the earth, are amongst the questions with which the geologist has to grapple in his higher capacity. These are problems which have occupied the attention of philosophers in every age of the world, and in periods long antecedent to the existence of a science of geology. The mere existence of cosmogonies in the religion of almost every nation, both ancient and modern, is a sufficient proof of the eager de- sire of the human mind to know something of the origin of the earth on which we tread. Every human being who has gazed on the vast panorama of the universe, though it may have been but with the eyes of a child, has felt the longing to solve, how- ever imperfectly, “the riddle of the painful earth,” and has, consciously or unconsciously, elaborated some sort of a theory as to the why and wherefore of what he sees. Apart from the profound and perhaps inscrutable problems which lie at the bottom of human existence, men have in all ages invented * Gr. palaios, ancient ; onta, beings ; Jogos, discourse. THE LAWS OF GEOLOGICAL ACTION. 3 theories to explain the common phenomena of the material universe ; and most of these theories, however varied in their details, turn out on examination to have a common root, and to be based on the same elements. Modern geology has its own theories on the same subject, and it will be well to glance for a moment at the principles underlying the old and the new views. It has been maintained, as a metaphysical hypothesis, that there exists in the mind of man an inherent principle, in virtue of which he believes and expects that what has been, will be ; and that the course of nature will be a continuous and unin- terrupted one. So far, however, from any such belief existing as a necessary consequence of the constitution of the human mind, the real fact seems to be that the contrary belief has been almost universally prevalent. In all old religions, and in the philosophical systems of almost all ancient nations, the order of the universe has been regarded as distinctly unstable, mutable, and temporary. A beginning and an end have always been assumed, and the course of terrestrial events between these two indefinite points has been regarded as liable to con- stant interruption by revolutions and catastrophes of different kinds, in many cases emanating from supernatural sources. Few of the more ancient theological creeds, and still fewer of the ancient philosophies, attained body and shape without containing, in some form or another, the belief in the existence of periodical convulsions, and of alternating cycles of destruc- tion and repair. That geology, in its early infancy, should have become im- bued with the spirit of this belief, is no more than might have been expected ; and hence arose the at one time powerful and generally-accepted doctrine of “ Catastrophism.” That the succession of phenomena upon the globe, whereby the earth’s crust had assumed the configuration and composition which we find it to possess, had been a discontinuous and broken succession, was the almost inevitable conclusion of the older geologists. Everywhere in their study of the rocks they met with apparently impassable gaps, and breaches of continuity that could not be bridged over. Everywhere they found them- selves conducted abruptly from one system of deposits to others totally different in mineral character or in stratigraphical position. Everywhere they discovered that well-marked and easily recognisable groups of animals and plants were succeeded, without the intermediation of any obvious lapse of time, by other assemblages of organic beings of a different character. Everywhere they found evidence that the earth’s crust had 4 PRINCIPLES OF PALAZONTOLOGY. undergone changes of such magnitude as to render it seemingly irrational to suppose that they could have been produced by any process now in existence. If we add to the above the prevalent belief of the time as to the comparative brevity of the period which had elapsed since the birth of the globe, we can readily understand the general acceptance of some form of catastrophism amongst the earlier geologists. As regards its general sense and substance, the doctrine of catastrophism held that the history of the earth, since first it emerged from the primitive chaos, had been one of periods of repose, alternating with catastrophes and cataclysms of a more or less violent character. The periods of tranquillity were sup- posed to have been long and protracted; and during each of them it was thought that one of the great geological ‘‘ forma- tions” was deposited. In each of these periods, therefore, the condition of the earth was supposed to be much the same as it is now—sediment was quietly accumulated at the bottom of the sea, and animals and plants flourished uninterruptedly in suc- cessive generations. Each period of tranquillity, however, was believed to have been, sooner or later, put an end to by a sudden and awful convulsion of nature, ushering in a brief and paroxysmal period, in which the great physical forces were unchained and permitted to spring into a portentous activity. The forces of subterranean fire, with their concomitant pheno- mena of earthquake and volcano, were chiefly relied upon as the efficient causes of these periods of spasm and revolution. Enormous elevations of portions of the earth’s crust were thus believed to be produced, accompanied by corresponding and equally gigantic depressions of other portions. In this way new ranges of mountains were produced, and previously exist- ing ranges levelled with the ground, seas were converted into dry land, and continents buried beneath the ocean—catastrophe following catastrophe, till the earth was rendered uninhabitable, and its races of animals and plants were extinguished, never to reappear in the same form. Finally, it was believed that this feverish activity ultimately died out, and that the ancient peace once more came to reign upon the earth. As the abnormal throes and convulsions began to be relieved, the dry land and sea once more resumed their relations of stability, the condi- tions of life were once more established, and new races of ani- mals and plants sprang into existence, to last until the super- vention of another fever-fit. Such is the past history of the globe, as sketched for us, in alternating scenes of fruittul peace and revolutionary destruc- tion, by the earlier geologists. As before said, we cannot THE LAWS OF GEOLOGICAL ACTION. 5 wonder at the former general acceptance of Catastrophistic doctrines. Even in the light of our present widely-increased knowledge, the series of geological monuments remains a broken and imperfect one ; nor can we ever hope to fill up completely the numerous gaps with which the geological record is defaced. Catastrophism was the natural method of accounting for these gaps, and, as we shall see, it possesses a basis of truth. At present, however, catastrophism may be said to be nearly ex- tinct, and its place is taken by the modern doctrine of ‘ Con- tinuity ” or “‘ Uniformity ””—a doctrine with which the name of Lyell must ever remain imperishably associated. The fundamental thesis of the doctrine of Uniformity is, that, in spite of all apparent violations of continuity, the se- quence of geological phenomena has in reality been a regular and uninterrupted one; and that the vast changes which can be shown to have passed over the earth in former periods have been the result of the slow and ceaseless working of the ordi- nary physical forces—acting with no greater intensity than they do now, but acting through enormously prolonged periods. The essential element in the theory of Continuity is to be found in the allotment of indefinite time for the accomplishment of the known series of geological changes. It is obviously the case, namely, that there are two possible explanations of all phenomena which lie so far concealed in “the dark backward and abysm of time,” that we can have no direct knowledge of the manner in which they were produced. We may, on the one hand, suppose them to be the result of some very powerful cause, acting through a short period of time. ‘That is Catas- trophism. Or, we may suppose them to be caused by a much weaker force operating through a proportionately prolonged period. ‘This is the viewof the Uniformitarians. It is a ques- tion of exergy versus ¢ime ; and it is “2me which is the true ele- ment of the case. An earthquake may remove a mountain in the course of a few seconds; but the dropping of the gentle rain will do the same, if we extend its operations over a millen- nium. And this is true of all agencies which are now at work, or ever have been at work, upon our planet. ‘The Catastro- phists, believing that the globe is but, as it were, the birth of yesterday, were driven of necessity to the conclusion that its history had been checkered by the intermittent action of par- oxysmal and almost inconceivably potent forces. The Unifor- mitarians, on the other hand, maintaining the “ adequacy of existing causes,” and denying that the known physical forces ever acted in past time with greater intensity than they do at present, are, equally of necessity, driven to the conclusion that 6 PRINCIPLES OF PALZONTOLOGY. the world is truly in its “hoary eld,” and that its present state is really the result of the tranquil and regulated action of known forces through unnumbered and innumerable centuries. The most important point for us, in the present connection, is the bearing of these opposing doctrines upon the question as to the origin of the existing terrestrial order. On any doc- trine of uniformity that order has been evolved slowly, and, according to law, from a pre-existing order. Any doctrine of catastrophism, on the other hand, carries with it, by implica- tion, the belief that the present order of things was brought about suddenly and irrespective of any pre-existent order; and it is important to hold clear ideas as to which of these beliefs is the true one. In the first place, we may postulate that the . world had a beginning, and, equally, that the existing terrestrial order had a beginning. However far back we may go, geology does not, and cannot, reach the actual beginning of the world; and we are, therefore, left simply to our own speculations on this point. With regard, however, to the existing terrestrial order, a great deal can be discovered, and to do so is one of the principal tasks of geological science. The first steps in the production of that order lie buried in the profound and un- searchable depths of a past so prolonged as to present itself to our finite minds as almost an eternity. The last steps are in the prophetic future, and can be but dimly guessed at. Be- tween the remote past and the distant future, we have, however, a long period which is fairly open to inspection ; and in saying a “long” period, it is to be borne in mind that this term is used in its geological sense. Within this period, enormously long as it is when measured by human standards, we can trace with reasonable certainty the progressive march of events, and can determine the laws of geological action, by which the pre- sent order of things has been brought about. The natural belief on this subject doubtless is, that the world, such as we now see it, possessed its present form and configuration from the beginning. Nothing can be more natural than the belief that the present continents and oceans have always been where they are now; that we have always had the same mountains and plains; that our rivers have always had their present courses, and our lakes their present positions ; that our climate has always been the same; and that our animals and plants have always been identical with those now familiar to us. Nothing could be more natural than such a belief, and nothing could be further removed from the actual truth On the contrary, a very slight acquaintance with geology shows us, in the words of Sir John Herschel, that THE LAWS OF GEOLOGICAL ACTION. vA “the actual configuration of our continents and islands, the coast-lines of our maps, the direction and elevation of our mountain-chains, the courses of our rivers, and the soundings of our oceans, are not things primordially arranged in the con- struction of our globe, but results of successive and complex actions on a former state of things; fat, again, of similar actions on another still more remote; and so on, till the ori- ginal and really permanent state is pushed altogether out of sight and beyond the reach even of imagination ; while on the other hand, a similar, and, as far as we can see, interminable vista is opened out for the future, by which the habitability of our planet is secured amid the total abolition on it of the present theatres of terrestrial life.” Geology, then, teaches us that the physical features which now distinguish the earth’s surface have been produced as the ultimate result of an almost endless succession of precedent changes. Palzontology teaches us, though not yet in such assured accents, the same lesson. Our present animals and plants have not been produced, in their innumerable forms, each as we now know it, as the sudden, collective, and simul- taneous birth of a renovated world. On the contrary, we have the clearest evidence that some of our existing animals and plants made their appearance upon the earth at a much earlier period than others. In the confederation of animated nature some races can boast of an immemorial antiquity, whilst others are comparative farvenus. We have also the clearest evidence that the animals and plants which now inhabit the globe have been preceded, over and over again, by other different assem- blages of animals and plants, which have flourished in succes- sive periods of the earth’s history, have reached their culmina- tion, and then have given way to a fresh series of living beings. We have, finally, the clearest evidence that these successive groups of animals and plants (faunze and floree) are to a greater or less extent directly connected with one another. Each group is, to a greater or less extent, the lineal descendant of the group which immediately preceded it in point of time, and is more or less fully concerned with giving origin to the group which immediately follows it. That this law of “ evolution” has prevailed to a great extent is quite certain ; but it does not meet all the exigencies of the case, and it is probable that its action has been supplemented by some still unknown law of a different character. We shall have to consider the question of geological “ con- tinuity” again. In the meanwhile, it is sufficient to state that this doctrine is now almost universally accepted as the basis 8 PRINCIPLES OF PALZONTOLOGY. of all inquiries, both in the domain of geology and that of paleontology. The advocates of continuity possess one im- mense advantage over those who believe in violent and revo- lutionary convulsions, that they call into play only agencies of which we have actual knowledge. We now that certain forces are now at work, producing certain modifications in the present condition of the globe; and we £zow that these forces are capable of producing the vastest of the changes which geology brings under our consideration, provided we assign a time proportionately vast for their operation. On the other hand, the advocates of catastrophism, to make good their views, are compelled to invoke forces and actions, both de- structive and restorative, of which we have, and can have, no direct knowledge. They endow the whirlwind and the earth- quake, the central fire and the rain from heaven, with powers as mighty as ever imagined in fable, and they build up the fragments of a repeatedly shattered world by the intervention of an intermittently active creative power. It should not be forgotten, however, that from one point of view there is a truth in catastrophism which is sometimes overlooked by the advocates of continuity and uniformity. Catastrophism has, as its essential feature, the proposition that the known and existing forces of the earth at one time acted with much greater intensity and violence than they do at pre- sent, and they carry down the »period of this excessive action to the commencement of the present terrestrial order. The Uniformitarians, in effect, deny this proposition, at any rate as regards any period of the earth’s history of which we have actual cognisance. If, however, the “nebular hypothesis” of the origin of the universe be well founded—as is generally ad- mitted—then, beyond question, the earth is a gradually cooling body, which has at one time been very much hotter than it is at present. There has been a time, therefore, in which the igneous forces of the earth, to which we owe the phenomena of earthquakes and volcanoes, must have been far more intensely active than we can conceive of from anything that we can see at the present day. By the same hypothesis, the sun is a cooling body, and must at one time have possessed a much higher temperature than it has at present. But increased heat of the sun would seriously alter the existing conditions affect- ing the evaporation and precipitation of moisture on our earth ; and hence the aqueous forces may also have acted at one time more powerfully than they do now. The fundamental prin- ciple of catastrophism is, therefore, not wholly vicious; and we have reason to think that there must have been periods— THE LAWS OF GEOLOGICAL ACTION. 9 very remote, it is true, and perhaps unrecorded in the history of the earth—in which the known physical forces may have acted with an intensity much greater than direct observation would lead us to imagine. And this may be believed, alto- gether irrespective of those great secular changes by which hct or cold epochs are produced, and which can hardly be called “catastrophistic,” as they are produced gradually, and are lable to recur at definite intervals. Admitting, then, that there zs a truth at the bottom of the once current doctrines of catastrophism, still it remains certain that the history of the earth has been one of /azw in all past time, as itis now. Nor need we shrink back affrighted at the vastness of the conception—the vaster for its very vagueness —that we are thus compelled to form as to the duration of geological time. As we grope our way backward through the dark labyrinth of the ages, epoch succeeds to epoch, and period to period, each looming more gigantic in its outlines and more shadowy in its features, as it rises, dimly revealed, from the mist and vapour of an older and ever-older past. It is useless to add century to century or millennium to millen- nium. When we pass a certain boundary-line, which, after all, is reached very soon, figures cease to convey to our finite faculties any real notion of the periods with which we have to deal. The astronomer can employ material illustrations to give form and substance to our conceptions of celestial space; but such a resource is unavailable to the geologist. The few thousand years of which we have historical evidence sink into absolute insignificance beside the unnumbered eons which unroll themselves one by one as we penetrate the dim recesses of the past, and decipher with feeble vision the pon- derous volumes in which the record of the earth is written. Vainly does the strained intellect seek to overtake an ever- receding commencement, and toil to gain some adequate grasp of an apparently endless succession. A beginning there must have been, though we can never hope to fix its point. Even speculation droops her wings in the attenuated atmosphere of a past so remote, and the light of imagination is quenched in the darkness of a history so ancient. In “me, as in space, the confines of the universe must ever remain concealed from us ; and of the end we know no more than of the beginning. In- conceivable as is to us the lapse of “ geological time,” it is no more than ‘“‘a mere moment of the past, a mere infinitesimal portion of eternity.” Well may “the human heart, that weeps and trembles,” say, with Richter’s pilgrim through celestial space, ‘‘I will go no farther; for the spirit of man acheth with IO PRINCIPLES OF PALAONTOLOGY. this infinity. Insufferable is the glory of God. Let me lie down in the grave, and hide me from the persecution of the Infinite, for end, I see, there is none.” CHAPTER F. THE SCOPE AND MATERIALS OF PALAZONTOLOGY. The study of the rock-masses which constitute the crust of the earth, if carried out in the methodical and scientific manner of the geologist, at once brings us, as has been before remarked, in contact with the remains or traces of living beings which formerly dwelt upon the globe. Such remains are found, in greater or less abundance, in the great majority of rocks; and they are not only of great interest in themselves, but they have proved of the greatest importance as throwing light upon vari- ous difficult problems in geology, in natural history, in botany, and in philosophy. Their study constitutes the science of paleontology; and though it is possible to proceed to a cer- tain length in geology and zoology without much palzontolo- gical knowledge, it is hardly possible to attain to a satisfac- tory general acquaintance with either of these subjects with- out having mastered the leading facts of the first. Similarly, it is not possible to study paleontology without some ac- quaintance with both geology and natural history. PALEONTOLOGY, then, is the science which treats of the living beings, whether animal or vegetable, which have in- habited the earth during past periods of its history. Its object is to eludicate, as far as may be, the structure, mode of exist- ence, and habits of all such ancient forms of life; to determine their position in the scale of organised beings; to lay down the geographical limits within which they flourished ; and to fix the period of their advent and disappearance. It is the ancient life-history of the earth ; and were its record complete, it would furnish us with a detailed knowledge of the form and relations of all the animals and plants which have at any period flourished upon the land-surfaces of the globe or inhabited its waters ; it would enable us to determine precisely their succes- sion in time; and it would place in our hands an unfailing key to the problems of evolution. Unfortunately, from causes which will be subsequently discussed, the palzontological record is extremely imperfect, and our knowledge is inter- THE SCOPE OF PALASONTOLOGY. Tt rupted by gaps, which not only bear a large proportion to our solid information, but which in many cases are of such a nature that we can never hope to fill them up. Foss1ts.—The remains of animals or vegetables which we now find entombed in the solid rock, and which constitute the working material of the paleeontologist, are termed “fossils,” * or “petrifactions.” In most cases, as can be readily under- stood, fossils are the actual hard parts of animals and plants which were in existence when the rock in which they are now found was being deposited. Most fossils, therefore, are of the nature of the shells of shell-fish, the skeletons of coral-zoophytes, the bones of vertebrate animals, or the wood, bark, or leaves of plants. All such bodies are more or less of a hard consist- ence to begin with, and are capable of resisting decay for a longer or shorter time—hence the frequency with which they occur in the fossil condition. Strictly speaking, however, by the term “fossil” must be understood “ any body, or the traces of the existence of any body, whether animal or vegetable, which has been buried in the earth by natural causes” (Lyell). We shall find, in fact, that many of the objects which we have to study as “fossils” have never themselves actually formed parts of any animal or vegetable, though they are due to the former existence of such organisms, and indicate what was the nature of these. Thus the footprints left by birds, or reptiles, or quadrupeds upon sand or mud, are just as much proofs of the former existence of these animals as would be bones, feathers, or scales, though in themselves they are inorganic. Under the head of fossils, therefore, come the footprints of air-breathing vertebrate animals; the tracks, trails, and bur- rows of sea-worms, crustaceans, or molluscs; the impressions left on the sand by stranded jelly-fishes ; the burrows in stone or wood of certain shell-fish; the “moulds” or “casts” of shells, corals, and other organic remains; and various other bodies of a more or less similar nature. FOssILISATION.—The term “fossilisation” is applied to all those processes through which the remains of organised beings may pass in being converted into fossils. These processes are numerous and varied ; but there are three principal modes of fossilisation which alone need be considered here. In the first instance, the fossil is to all intents and purposes an actual portion of the original organised being—such as a bone, a shell, or a piece of wood. In some rare instances, as in the case of the body of the Mammoth discovered embedded in ice at the mouth of the Lena in Siberia, the fossil may be preserved * Lat. fossus, dug up. 2 PRINCIPLES OF PALASONTOLOGY. almost precisely in its original condition, and even with its soft parts uninjured. More commonly, certain changes have taken place in the fossil, the principal being the more or less total removal of the organic matter originally present. Thus bones become light and porous by the removal of their gela- tine, so as to cleave to the tongue on being applied to that organ; whilst shells become fragile, and lose their primitive colours. In other cases, though practically the real body it represents, all the cavities of the fossil, down to its minutest recesses, may have become infiltrated with mineral matter. It need hardly be added, that it is in the more modern rocks that we find the fossils, as a rule, least changed from their former condition; but the original structure is often more or less com- pletely retained in some of the fossils from even the most ancient formations. In the second place, we very frequently meet with fossils in the state of “casts” or moulds of the original organic body. What occurs in this case will be readily understood if we ima- gine any common bivalve shell, as an Oyster, or Mussel, or Cockle, embedded in clay or mud. If the clay were sufficiently soft and fluid, the first thing would be that it would gain access to the interior of the shell, and would completely fill up the space between the valves. The pressure, also, of the surround- ing matter would insure that the clay would everywhere ad- here closely to the exterior of the shell. If now we suppose the clay to be in any way hardened so as to be converted into stone, and if we were to break up the stone, we should obvi- ously have the following state of parts. The clay which filled the shell would form an accurate cast of the zwfertor of the shell, and the clay outside would give us an exact impression or cast of the exterior of the shell (fig. 1). We should have, then, two casts, an interior and an exterior, and the two would be very different to one another, since the inside of a shell is very unlike the outside. In the case, in fact, of many uni- valve shells, the interior cast or “mould” is so unlike the ex- , terior cast, or unlike the shell Fig. 1.—Trigonia longa, showing casts itself, that it may be difficult to ae aon of the shell— determine the true origin of the former. It only remains to add that there is sometimes a further complication. If the rock be very porous and permeable by THE SCOPE OF PALAHONTOLOGY. 13 water, it may happen that the original shell is entirely dissolved away, leaving the interior cast loose, like the kernel of a nut, within the case formed by the exterior cast. Or it may happen that subsequent to the attainment of this state of things, the space thus left vacant between the interior and exterior cast— the space, that is, formerly occupied by the shell itself—may be filled up by some foreign mineral deposited there by the infiltration of water. In this last case the splitting open of the rock would reveal an interior cast, an exterior cast, and finally a body which would have the exact form of the original shell, but which would be really a much later formation, and which would not exhibit under the microscope the minute structure of shell. In the third class of cases we have fossils which present with the greatest accuracy the external form, and even some- times the internal minute structure, of the original organic body, but which, nevertheless, are not themselves truly organic, but have been formed by a ‘‘ replacement” of. the particles of the primitive organism by some mineral substance. The most elegant example of this is afforded by fossil wood which has been “ silicified” or converted into flint (sz/ex). In such cases we have fossil wood which presents the rings of growth and fibrous structure of recent wood, and which under the micro- scope exhibits the minutest vessels which characterise ligneous tissue, together with the even more minute markings of the vessels (fig. 2). The whole, however, instead of being com- E b | bts ° sare ©} id Ion) i a IL GIOWS Me lo e a4 x Ke G iz ce} G [el S} aig sof 9 wake | a) © ao si Fig. 2.— Microscopic section of the Fig. 3.—Microscopic section of the wood silicified wood of a Conifer (Seguota) cut of the common Larch (A dies darix), cut in in the long direction of the fibres. Post- the long direction of the fibres. In boththe tertiary? Colorado. (Original.) fresh and the fossil wood (fig. 2) are seen the discs characteristic of coniferous wood. (Original. ) posed of the original carbonaceous matter of the wood, is now converted into flint. The only explanation that can be given 14 PRINCIPLES OF PALAZZONTOLOGY. of this by no means rare phenomenon, is that the wood must have undergone a slow process of decay in water charged with silica or flint in solution. As each successive particle of wood was removed by decay, its place was taken by a particle of flint deposited from the surrounding water, till ultimately the entire wood was silicified. The process, therefore, resembles what would take place if we were to pull down a house built of brick by successive bricks, replacing each brick as removed by a piece of stone of precisely the same size and form. ‘The result of this would be that the house would retain its primi- tive size, shape, and outline, but it would finally have been converted from a house of brick into a house of stone. Many other fossils besides wood—such as shells, corals, sponges, &c.—are often found silicified; and this may be regarded as the commonest form of fossilisation by replacement. In other cases, however, though the principle of the process is the same, the replacing substance may be iron pyrites, oxide of iron, sulphur, malachite, magnesite, talc, &c.; but it is rarely that the replacement with these minerals is so perfect as to preserve the more delicate details of internal structure. CHAPTER: if. THE FOSSTILIFEROUS ROCKS. Fossils are found in rocks, though not universally or pro- miscuously ; and it is therefore necessary that the paleonto- logist should possess some acquaintance with, at any rate, those rocks which yield organic remains, and which are therefore said to be “ fossiliferous.” In geological language, all the materials which enter into the composition of the solid crust of the earth, be their texture what it may—from the most im- palpable mud to the hardest granite—are termed “ rocks ;” and for our present purpose we may divide these into two great groups. In the first division are the Zegweous Rocks—such as the lavas and ashes of voleanoes—which are formed within the body of the earth itself, and which owe their structure and origin to the action of heat. The Igneous Rocks are formed primarily below the surface of the earth, which they only reach as the result of volcanic action ; they are generally destitute of distinct ‘‘ stratification,” or arrangement in successive layers ; and they do not contain fossils, except in the comparatively THE FOSSILIFEROUS ROCKS. 15 rare instances where volcanic ashes have enveloped animais or plants which were living in the sea or on the land in the immediate vicinity of the volcanic focus. The second great division of rocks is that of the Fossiliferous, Aqueous, or Sedi- mentary Rocks. These are formed at the surface of the earth, and, as implied by one of their names, are invariably deposited in water. They are produced by vital or chemical action, or are formed from the “sediment” produced by the disintegra- tion and reconstruction of previously existing rocks, without previous solution ; they mostly contain fossils; and they are arranged in distinct layers or “strata.” The so-called “aerial” rocks which, like beds of blown sand, have been formed by the action of the atmosphere, may also contain fossils; but they are not of such importance as to require special notice here. For all practical purposes, we may consider that the Aque- ous Rocks are the natural cemetery of the animals and plants of bygone ages; and it is therefore essential that the palezon- tological student should be acquainted with some of the prin- cipal facts as to their physical characters, their minute structure and mode of origin, their chief varieties, and their historical succession. . The Sedimentary or Fossiliferous Rocks form the greater portion of that part of the earth’s crust which is open to our examination, and are distinguished by the fact that they are regularly “stratified” or arranged in distinct and definite layers or “strata.” These layers may consist of a single material, as in a block of sandstone, or they may consist of different materials. When examined on a large scale, they are always found to consist of alternations of layers of different mineral composition. We may examine any given area, and find in it nothing but one kind of rock—sandstone, perhaps, or lime- stone. In all cases, however, if we extend our examination sufficiently far, we shall ultimately come upon different rocks; and, as a general rule, the thickness of any particular set of beds is comparatively small, so that different kinds of rock alternate with one another in comparatively small spaces. As regards the origin of the Sedimentary Rocks, they are for the most part “ derivative” rocks, being derived from the wear and tear of pre-existent rocks. Sometimes, however, they owe their origin to chemical or vital action, when they would more properly be spoken of simply as Aqueous Rocks. As to their mode of deposition, we are enabled to infer that the materials which compose them have formerly been spread out by the action of water, from what we see going on every day 16 PRINCIPLES OF PALZONTOLOGY. at the mouths of our great rivers, and on a smaller scale wher- ever there is running water. Every stream, where it runs into = ——————__.._— Fig. 4.—Sketch of Carboniferous strata at Kinghorn, in Fife, showing stratified beds (limestone and shales) surmounted by an unstratified mass of trap. (Original.) a lake or into the sea, carries with it a burden of mud, sand, and rounded pebbles, derived from the waste of the rocks which form its bed and banks. When these materials cease to be impelled by the force of the moving water, they sink to the bottom, the heaviest pebbles, of course, sinking first, the smaller pebbles and sand next, and the finest mud last. Ulti- mately, therefore, as might have been inferred upon theoretical grounds, and as is proved by practical experience, every lake becomes a receptacle for a series of stratified rocks produced by the streams flowing into it. These deposits may vary in different parts of the lake, according as one stream brought down one kind of material and another stream contributed another material ; but in all cases the materials will bear ample evidence that they were produced, sorted, and deposited by running water. The finer beds of clay or sand will all be arranged in thicker or thinner layers or laminz ; and if there are any beds of pebbles these will all be rounded or smooth, just like the water-worn pebbles of any brook-course. In all probability, also, we should find in some of the beds the re- THE FOSSILIFEROUS ROCKS. 17 mains of fresh-water shells or plants or other organisms which inhabited the lake at the time these beds were being de- posited. In the same way large rivers—such as the Ganges or Mississippi—deposit all the materials which they bring down at their mouths, forming in this way their ‘deltas.’ When- ever such a delta is cut through, either by man or by some channel of the river altering its course, we find that it is com- posed of a succession of horizontal layers or strata of sand or mud, varying in mineral composition, in structure, or in grain, according to the nature of the materials brought down by the river at different periods. Such deltas, also, will contain the remains of animals which inhabit the river, with fragments of the plants which grew on its banks, or bones of the animals which lived in its basin. Nor is this action confined, of course, to large rivers only, though naturally most conspicuous in the greatest bodies of water. On the contrary, all streams, of whatever size, are engaged in the work of wearing down the dry land, and of transporting the materials thus derived from higher to lower levels, never resting in this work till they reach the sea. Yili, Fig. 5.—Diagram to illustrate the formation of sedimentary deposits at the point where a river debouches into the sea. Lastly, the sea itself—irrespective of the materials delivered into it by rivers—is constantly preparing fresh stratified de- B 18 PRINCIPLES OF PALAZONTOLOGY. posits by its own action. Upon every coast-line the sea is constantly eating back into the land and reducing its com- ponent rocks to form the shingle and sand which we see upon every shore. The materials thus produced are not, however, lost, but are ultimately deposited elsewhere in the form of new stratified accumulations, in which are buried the remains of animals inhabiting the sea at the time. Whenever, then, we find anywhere in the interior of the land any series of beds having these characters—composed, that is, of distinct layers, the particles of which, both large and small, show distinct traces of the wearing action of water—whenever and wherever we find such rocks, we are justified in assuming that they have been deposited by water in the manner above mentioned. Either they were laid down in some former lake by the combined action of the streams which flowed into it; or they were deposited at the mouth of some ancient river, forming its delta; or they were laid down at the bottom of the ocean. In the first two cases, any fossils which the beds might contain would be the remains of fresh-water or terres- trial organisms. In the last case, the majority, at any rate, of the fossils would be the remains of marine animals. The term “ formation” is employed by geologists to express “any group of rocks which have some character in common, whether of origin, age, or composition” (Lyell); so that we may speak of stratified and unstratified formations, aqueous or igneous formations, fresh-water or marine formations, and so on. CHIEF DIVISIONS OF THE AQUEOUS ROCKS. The Aqueous Rocks may be divided into two great sections, the Mechanically-formed and the Chemically-formed, includ- ing under the last head all rocks which owe their origin to vital action, as well as those produced by ordinary chemical agencies. A. MECHANICALLY-FORMED Rocks. — These are all those Aqueous Rocks of which we can obtain proofs that their particles have been mechanically transported to their present situation. Thus, if we examine a piece of conglomerate or puddingstone, we find it to be composed of a number of rounded pebbles embedded in an enveloping matrix or paste, which is usually of a sandy nature, but may be composed ot carbonate of lime (when the rock is said to be a “ calcareous conglomerate”). The pebbles in all conglomerates are worn and rounded by the action of water in motion, and thus show THE FOSSILIFEROUS ROCKS. I9 that they have been subjected to much mechanical attrition, whilst they have been mechanically transported for a greater or less distance from the rock of which they originally formed part. The analogue of the old.conglomerates at the present day is to be found in the great beds of shingle and gravel which are formed by the action of the sea on every coast-line, and which are composed of water-worn and well-rounded pebbles of different sizes. A dveccia is a mechanically-formed rock, very similar to a conglomerate, and consisting of larger or smaller fragments of rock embedded in a common matrix. The fragments, however, are in this case all more or less angular, and are not worn or rounded. The fragments in breccias may be of large size, or they may be comparatively small (fig. 6); and the matrix may be composed of sand (aren- aceous) or of carbonate of lime (calcareous). In the case ofan ordinarysandstone, again, we have a rock which may be regarded as simply a very fine- grained conglomerate or brec- cia, being composed of small grains of sand (silica), some- timesrounded, sometimes more or less angular, cemented to- gether by some such substance as oxide of iron, silicate of iron, or carbonate of lime. A RES: sandstone, therefore, like a Fig. 6.—Microscopic section of a calcare- eouglénicratey’ is -a-mechaini-’ guy beoudin tes Lowe Silman (Coniston cally-formed rock, its Compo- The fragments are all of small size, and : : consist of angular pieces of transparent nent grains being equally the quartz, volcanic ashes, and limestone em- result of mechanical attrition bedded ina matrix of crystalline limestone. ; (Original. ) ' and having equally been trans- ported from a distance; and the same is true of the ordinary sand of the sea-shore, which is nothing more than an uncon- solidated sandstone. Other so-called sands and sandstones, though equally mechanical in their origin, are truly calcareous in their nature, and are more or less entirely composed of carbonate of lime. Of this kind are the shell-sand so com- mon on our coasts, and the coral-sand which is so largely formed in the neighbourhood of coral-reefs. In these cases the rock is composed of fragments of the skeletons of shell- fish, and numerous other marine animals, together, in many instances, with the remains of certain sea-weeds (Corallines, Nullipores, &c.) which are endowed with the power of secret- 20 PRINCIPLES OF PALZ ONTOLOGY. ing carbonate of lime from the sea-water. Lastly, in cer- tain rocks still finer in their texture than sandstones, such as the various mud-rocks and shales, we can still recognise a mechanical source and origin. If slices of any of these rocks sufficiently thin to be transparent are examined under the microscope, it will be found that they are composed of minute grains of different sizes, which are all more or less worn and rounded, and which clearly show, therefore, that they have been subjected to mechanical attrition. All the above-mentioned rocks, then, are mechanically-formed rocks; and they are often spoken of as “ Derivative Rocks,” in consequence of the fact that their particles can be shown to have been mechanically derzved from other pre-existent rocks. It follows from this that every bed of any mechanically-formed rock is the measure and equivalent of a corresponding amount of destruction of some older rock. It is not necessary to enter here into a minute account of the subdivisions of these rocks, but it may be mentioned that they may be divided into two principal groups, according to their chemical composition. In the one group we have the so-called Avenaceous (Lat. arena, sand) or S7/iceous Rocks, which are essentially composed of larger or smaller grains of flint or silica. In this group are comprised ordinary sand, the varieties of sandstone and grit, and most conglomerates and breccias. We shall, however, after- wards see that some siliceous rocks are of organic origin. In the second group are the so-called Argillaceous (Lat. argilla, clay) Rocks, which contain a larger or smaller amount of clay or hydrated silicate of alumina in their composition. Under this head come clays, shales, marls, marl-slate, clay-slates, and most flags and flagstones. B. CHEMICALLY-FORMED Rocks.—In this section are com- prised all those Aqueous or Sedimentary Rocks which have been formed by chemical agencies. As many of these chemi- cal agencies, however, are exerted through the medium of living beings, whether animals or plants, we get into this section a number of what may be called “ orvganically-formed rocks.” These are of the greatest possible importance to the palzontologist, as being to a greater or less extent composed of the actual remains of animals or vegetables, and it will therefore be necessary to consider their character and struc- ture in some detail. By far the most important of the chemically-formed rocks are the so-called Calcareous Rocks (Lat. calx, lime), com- prising all those which contain a large proportion of carbonate of lime, or are wholly composed of this substance. Carbonate THE FOSSILIFEROUS ROCKS. 21 of lime is soluble in water holding a certain amount of car- bonic acid gas in solution ; and it is, therefore, found in larger or smaller quantity dissolved in all natural waters, both fresh and salt, since these waters are always to some extent charged with the above-mentioned solvent gas. A great number of aquatic animals, however, together with some aquatic plants, are endowed with the power of separating the lime thus held in solution in the water, and of reducing it again to its solid condition. In this way shell-fish, crustaceans, sea-urchins, corals, and an immense number of other animals, are enabled to construct their skeletons ; whilst some plants form hard structures within their tissues in a precisely similar manner. We do meet with some calcareous deposits, such as the “stalactites” and “stalagmites” of caves, the ‘“ calcareous tufa” and “‘travertine” of some hot springs, and the spongy calcareous deposits of so-called “petrifying springs,” which are purely chemical in their origin, and owe nothing to the operation of living beings. Such deposits are formed simply by the precipitation of carbonate of lime from water, in con- sequence of the evaporation from the water of the carbonic acid gas which formerly held the lime in solution ; but, though sometimes forming masses of considerable thickness and of geological importance, they do not concern us here. Almost all the limestones which occur in the series of the stratified rocks are, primarily at any rate, of organic origin, and have been, directly or indirectly, produced by the action of certain lime-making animals or plants, or both combined. ‘The pre- sumption as to all the calcareous rocks, which cannot be clearly shown to have been otherwise produced, is that they are thus organically formed ; and in many cases this presump- tion can be readily reduced to a certainty. There are many varieties of the calcareous rocks, but the following are those which are of the greatest importance :— Chalk is a calcareous rock of a generally soft and pulver- ulent texture, and with an earthy fracture. It varies in its purity, being sometimes almost wholly composed of carbonate of lime, and at other times more or less intermixed with foreign matter. Though usually soft and readily reducible to powder, chalk is occasionally, as in the north of Ireland, tolerably hard and compact; but it never assumes the crystalline aspect and stony density of limestone, except it be in immediate contact with some mass of igneous rock. By means of the microscope, the true nature and mode of formation of chalk can be determined with the greatest ease. In the case of the harder varieties, the examination can be conducted by means 22 PRINCIPLES OF PALZONTOLOGY. of slices ground down to a thinness sufficient to render them transparent ; but in the softer kinds the rock must be disinte- grated under water, and the aébris examined microscopically. When investigated by either of these methods, chalk is found to be a genuine organic rock, being composed of the shells or hard parts of innumerable marine animals of different kinds, some entire, some fragmentary, cemented together by a matrix of very finely granular carbonate of lime. Foremost amongst the animal remains which so largely compose chalk are the shells of the minute creatures which will be subsequently spoken of under the name of Foraminifera (fig. 7), and which, in spite of their microscopic dimensions, play a more im- portant part in the process of lime-making than perhaps any other of the larger inhabitants of the ocean. As chalk is found in beds of hundreds of feet in thick- ness, and of great purity, there was long felt much difficulty in satisfactorily accounting for its mode of formation and ori- gin. By the researches of Carpenter, Wyville Thomson, Fig. 7.—Section of Gravesend Chalk, Huxley, Wallich, and others, examined by transmitted light and highly .- magnified. Besides the entire shells of it has, however, been shown Cubierrina, Retela, ond Textulerie that there is now forming, in gerina are seen. (Original.) the profound depths of our great oceans, a deposit which is in all essential respects identical with chalk, and which is generally known as the “ Atlantic ooze,” from its having been first discovered in that sea. This ooze is found at great depths (5000 to over 15,000 feet) in both the Atlantic and Pacific, covering enormously large areas of the sea-bottom, and it presents itself as a whitish-brown, sticky, impalpable mud, very like greyish chalk when dried. Chemical examination shows that the ooze is composed almost wholly of carbonate of lime, and microscopical examination proves it to be of organic origin, and to be made up of the remains of living beings. The principal forms of these belong to the Foraminifera, and the commonest of these are the irregularly-chambered shells of Globigerina, absolutely indistinguishable from the Globigerine which are so largely present in the chalk (fig. 8). Along with these occur fragments of the skeletons of other larger creatures, THE FOSSILIFEROUS ROCKS. 23 and a certain proportion of the flinty cases of minute animal and vegetable organisms (Polycystina and Diatoms). ‘Though many of the minute animals, the hard parts of which form the ooze, undoubtedly live at or near the surface of the sea, others, probably, really live near the bottom ; and the ooze itself forms a congenial home for numerous sponges, sea- lilies, and other marine ani- mals which flourish at great depths in the sea. There is thus established an intimate and most interesting parallel- ism between the chalk and Fig. 8.—Organisms in the Atlantic Ooze, che ooze of modern oceans. chiefly Foraminifera (Globigerina and : : Textularia), with Polycystina and sponge- Both are formed essentially 1n spicules; highly magnified. (Original.) the same way, and the latter only requires consolidation to become actually converted into chalk. Both are fundamentally organic deposits, apparently requiring a great depth of water for their accumulation, and mainly composed of the remains of Foraminifera, together with the entire or broken skeletons of other marine animals of greater dimensions. It is to be remembered, however, that the ooze, though strictly representative of the chalk, cannot be said in any proper sense to be actually zdentical with the for- mation so called by geologists. A great lapse of time separates the two, and though composed of the remains of representative classes or groups of animals, it is only in the case of the lowly- organised Glodigering, and of some other organisms of little higher grade, that we find absolutely the same kinds or secces of animals in both. Limestone, \ike chalk, is composed of carbonate of lime, sometimes almost pure, but more commonly with a greater or less intermixture of some foreign material, such as alumina or silica. The varieties of limestone are almost innumerable, but the great majority can be clearly proved to agree with chalk in being essentially of organic origin, and in being more or less largely composed of the remains of living beings. In many instances the organic remains which compose limestone are so large as to be readily visible to the naked eye, and the rock is at once seen to be nothing more than an agglomera- tion of the skeletons, generally fragmentary, of certain marine animals, cemented together by a matrix of carbonate of lime. 24 -PRINCIPLES OF PALEONTOLOGY. This is the case, for example, with the so-called ‘“ Crinoidal Limestones ” and “ Encrinital Marbles” with which the geolo- gist is so familiar, especially as occurring in great beds amongst the older formations of the earth’s crust. ‘These are seen, on weathered or broken surfaces, or still better in polished slabs (fig. 9), to be composed more or less exclusively of the broken Fig. 9 —Slab of Crinoidal marble, from the Carboniferous limestone of Dent, in York- shire, of the natural size. The polished surface intersects the columns of the Crinoids at different angles, and thus gives rise to varying appearances. (Original.) stems and detached plates of sea-lilies (Crinoids). Similarly, other limestones are composed almost entirely of the skeletons of corals; and such old coralline limestones can readily be paralleled by formations which we can find in actual course of production at the present day. We only need to transport ourselves to the islands of the Pacific, to the West Indies, or to the Indian Ocean, to find great masses of lime formed simi- larly by living corals, and well known to every one under the name of “coral-reefs.” Such reefs are often of vast extent, both superficially and in vertical thickness, and they fully equal in this respect any of the coralline limestones of bygone ages. Again, we find other limestones—such as the celebrated ‘“Nummulitic Limestone” (fig. 10), which sometimes attains a thickness of some thousands of feet—which are almost entirely made up of the shells of Foraminifera. In the case of the ‘““Nummulitic Limestone,” just mentioned, these shells are of large size, varying from the size of a split pea up to that ofa THE FOSSILIFEROUS ROCKS. 25 florin. There are, however, as we shall see, many other lime- stones, which are likewise largely made up of Foraminifera, Fig. 1o.—Piece of Nummulitic Limestone from the Great Pyramid. Of the natural size. (Original.) but in which the shells are very much more minute, and would hardly be seen at all without the microscope. We may, in fact, consider that the great agents in the pro- duction of limestones in past ages have been animals belonging to the Cvinoids, the Corads, and the Foraminifera. At the pre- sent day, the Crinoids have been nearly extinguished, and the few known survivors seem to have retired to great depths in the ocean ; but the two latter still actively carry on the work of lime-making, the former being very largely helped in their operations by certain lime-producing marine plants (JVud/ipores and Corallines). We have to remember, however, that though the limestones, both ancient and modern, that we have just spoken of, are truly organic, they are not necessarily formed out of the remains of animals which actually lived on the precise spot where we now find the limestone itself. We may find a crinoidal limestone, which we can show to have been actually formed by the successive growth of generations of sea-lilies 2 place ; but we shall find many others in which the rock is made up of innumerable fragments of the skeletons of these creatures, which have been clearly worn and rubbed by the sea-waves, and which have been mechanically transported to their present site. In the same way, a limestone may be shown to have been an actual coral-reef, by the fact that we find in it great masses of coral, growing in their natural posi- 26 PRINCIPLES OF PALZONTOLOGY. tion, and exhibiting plain proofs that they were simply quietly buried by the calcareous sediment as they grew; but other limestones may contain only numerous rolled and water-worn fragments of corals, This is precisely paralleled by what we can observe in our existing coral-reefs. Parts of the modern coral-islands and coral-reefs are really made up of corals, dead or alive, which actually grew on the spot where we now find them; but other parts are composed of a limestone-rock (“coral- rock”), or of a loose sand (“coral-sand”), which is organic in the sense that it is composed of lime formed by living beings, but which, in truth, is composed of fragments of the skeletons of these living beings, mechanically trans- ported and heaped together by the sea. To take another example nearer home, we may find great accumulations of calcareous matter formed in place, by the growth of shell-fish, such as oysters or mussels ; but we can also find equally great accumulations on many of our shores in the form of “ shell- sand,” which is equally composed of the shells of molluscs, but which is formed by the trituration of these shells by the mechanical power of the sea-waves. We thus see that though all these limestones are primarily organic, they not uncom- monly become ‘‘mechanically-formed” rocks in a secondary sense, the materials of which they are composed being formed by living beings, but having been mechanically transported to the place where we now find them. Many limestones, as we have seen, are composed of large and conspicuous organic remains, such as strike the eye at once. Many others, however, which at first sight appear com- pact, more or less crystalline, and nearly devoid of traces of life, are found, when properly examined, to be also composed of the remains of various organisms. All the commoner lime- stones, in fact, from the Lower Silurian period onwards, can be easily proved to be thus organic rocks, if we investigate weathered or polished surfaces with a lens, or, still better, if we cut thin slices of the rock and grind these down till they are transparent. When thus examined, the rock is usually found to be composed of innumerable entire or fragmentary fossils, cemented together by a granular or crystalline matrix of carbonate of lime (figs. 11 and 12). When the matrix is granular, the rock is precisely similar to chalk, except that it is harder and less earthy in texture, whilst the fossils are only occasionally referable to the Foraminifera. In other cases, the matrix is more or less crystalline, and when this crystallisa- tion has been carried to a great extent, the original organic nature of the rock may be greatly or ‘completely obscured THE FOSSILIFEROUS ROCKS. 27 thereby. Thus, in limestones which have been greatly altered or “metamorphosed” by the combined action of heat and pres- Fig. 11.—Section of Carboniferous Fig. 12.—Section of Coniston Limestone Limestone from Spergen Hill, Indiana, (Lower Silurian) from Keisley, Westmore- U.S., showing numerous large-sized land; magnified. The matrix 1s very coarse- Foraminifera (Endothyra) and a few ly crystalline, and the included organic re- oolitic grains ; magnified. (Original.) meee chiefly stems of Crinoids. (Ori- ginal. sure, all traces of organic remains become annihilated, and the rock becomes completely crystalline throughout. This, for example, is the case with the ordinary white “statuary marble,” slices of which exhibit under the microscope nothing but an ageregate of beautifully transparent crystals of carbonate of lime, without the smallest traces of fossils. ‘There are also other cases, where the limestone is not necessarily highly crystalline, and where no metamorphic action in the strict sense has taken place, in which, nevertheless, the microscope fails to reveal any evidence that the rock is organic. Such cases are somewhat obscure, and doubtless depend on differ- ent causes in different instances; but they do not affect the important generalisation that limestones are fundamentally the product of the operation of living beings. This fact remains certain; and when we consider the vast superficial extent occupied by calcareous deposits, and the enormous collective thickness of these, the mind cannot fail to be impressed with the immensity of the period demanded for the formation of these by the agency of such humble and often microscopic creatures as Corals, Sea-lilies, Foraminifers, and Shell-fish. Amongst the numerous varieties of limestone, a few are of such interest as to deserve a brief notice. A/agnestan limestone- or dolomite, differs from ordinary limestone in containing a cer- tain proportion of carbonate of magnesia along with the carbon, ate of lime. The typical dolomites contain a large proportion of 28 PRINCIPLES OF PALAZONTOLOGY. carbonate of magnesia, and are highly crystalline. The ordi- nary magnesian limestones (such as those of Durham in the Permian series, and the Guelph Limestones of North America in the Silurian series) are generally of a yellowish, buff, or brown colour, with a crystalline or pearly aspect, effervescing with acid much less freely than ordinary limestone, exhibiting numerous cavities from which fossils have been dissolved out, and often assuming the most varied and singular forms in con- sequence of what is called “ concretionary action.” Examina- tion with the microscope shows that these limestones are composed of an aggregate of minute but perfectly distinct crystals, but that minute organisms of different kinds, or fragments of larger fossils, are often present as well. Other magnesian limestones, again, exhibit no striking external pecu- liarities by which the presence of magnesia would be readily recognised, and though the base of the rock is crystalline, they are replete with the remains of organised beings. Thus many of the magnesian limestones of the Carboniferous series of the North of England are very like ordinary limestone to look at, though effervescing less freely with acids, and the microscope proves them to be charged with the remains of Foraminifera and other minute organisms. Marbles are of various kinds, all limestones which are suffi- ciently hard and compact to take a high polish going by this name. Statuary marble, and most of the celebrated foreign marbles, are “metamorphic” rocks, of a highly crystalline nature, and having all traces of their .primitive organic struc- ture obliterated. Many other marbles, however, differ from ordinary limestone simply in the matter of density. Thus, many marbles (such as Derbyshire marble) are simply ‘cri- noidal limestones” (fig. 9); whilst various other British marbles exhibit innumerable organic remains under the mi- croscope. Black marbles owe their colour to the presence of very minute particles of carbonaceous matter, in some cases at any rate; and they may either be metamorphic, or they may be charged with minute fossils such as Aovaminifera (ag., the black limestones of Ireland, and the black marble of Dent, in Yorkshire). “ Oolitic” Limestones, or “ oolites,” as they are often called, are of interest both to the paleontologist and geologist. The peculiar structure to which they owe their name is that the rock is more or less entirely composed of spheroidal or oval grains, which vary in size from the head of a small pin or less up to the size of a pea, and which may be in almost immediate contact with one another, or may be cemented together by a THE FOSSILIFEROUS ROCKS. 29 more or less abundant calcareous matrix. When the grains | are pretty nearly spherical and are in tolerably close contact, the rock looks very like the roe of a fish, and the name of “ oolite” or “ egg-stone” is in allusion to this. When the grains are of the size of peas or upwards, the rock is often called a “pisolite” (Lat. pzswm, a pea). Limestones having this peculiar structure are especially abundant in the Jurassic formation, which is often called the ‘‘ Oolitic series ” for this reason ; but essentially similar limestones occur not uncom- monly in the Silurian, Devonian, and Carboniferous forma- tions, and, indeed, in almost all rock-groups in which limestones are largely developed. Whatever may be the age of the for- mation in which they occur, and whatever may be the size of their component “ eggs,” the structure of oolitic limestones is fundamentally the same. All the ordinary oolitic limestones, namely, consist of little spherical or ovoid “ concretions,” as they are termed, cemented together by a larger or smaller amount of crystalline carbonate of lime, together, in many instances, with numerous organic remains of different kinds (fig. 13). When examined in polished slabs, or in thin sec- tions prepared for the micro- scope, each of these little con- cretions is seen to consist of numerous concentric coats of carbonate of lime, which some- times simply surround an ima- ginary centre, but which, more commonly, have been suc- cessively deposited round some foreign body, such as a little crystal of quartz, a clus- ter of sand-grains, or a minute shell. In other cases, as in ULL some of the beds of the Car- Fig. 13.—Slice of oolitic limestone boniferous limestone in the LM ent aoe oe a North of England, where the limestone is highly “‘arenaceous,” there is a modification of the oolitic structure. Microscopic sections of these sandy lime- stones (fig. 14) show numerous generally angular or oval grains of silica or flint, each of which is commonly surrounded by a thin coating of carbonate of lime, or sometimes by several such coats, the whole being cemented together along with the shells of Foraminifera and other minute fossils by a matrix of crystal- line calcite. As compared with typical oolites, the concretions in these limestones are usually much more irregular in shape, 30 PRINCIPLES OF PALAZONTOLOGY. often lengthened out and almost cylindrical, at other times angular, the central nucleus being of large size, and the sur- rounding envelope of lime be- ing very thin, and often exhib- iting no concentric structure. In both these and the ordinary oolites, the structure is funda- mentally the same. Both have been formed in a sea, probably of no great depth, the waters of which were charged with carbonate of lime in solution, whilst the bottom was formed of sand intermixed with minute shells and fragments of the Fig. 14.—Slice of arenaceous and Skeletons of larger marine ani- oolitic limestone from the Carbonifer- mals. The excess of lime in ous series of Shap, Westmoreland; mag- mu nified. The section also exhibits Fora- the sea-water was precipitated a and other minute fossils. (Ori- Poncee san d-grains, or round the smaller shells, as so many nuclei, and this precipitation must often have taken place time after time, so as to give rise to the concentric structure so char- acteristic of oolitic concretions. Finally, the oolitic grains thus produced were cemented together by a further precipitation of crystalline carbonate of lime from the waters of the ocean. Phosphate of Lime is another lime-salt, which is of interest to the paleontologist. It does not occur largely in the strati- fied series, but it is found in considerable beds * in the Laurentian formation, and less abundantly in some later rock- groups, whilst it occurs abundantly in the form of nodules in parts of the Cretaceous (Upper Greensand) and Tertiary deposits. Phosphate of lime forms the larger proportion of the earthy matters of the bones of Vertebrate animals, and also occurs in less amount in the skeletons of certain of the Inver- tebrates (¢.¢., Crustacea). It is, indeed, perhaps more dis- tinctively than carbonate of lime, an organic compound ; and though the formation of many known deposits of phosphate of * Apart from the occurrence of phosphate of lime in actual beds in the stratified rocks, as in the Laurentian and Silurian series, this salt may also occur disseminated through the rock, when it can only be detected by chemical analysis. It is interesting to note that Dr Hicks has recently proved the occurrence of phosphate of lime in this disseminated form in rocks as old as the Cambrian, and that in quantity quite equal to what is generally found to be present in the later fossiliferous rocks. This affords a chemical proof that animal life flourished abundantly in the Cambrian seas. THE FOSSILIFEROUS ROCKS. 31 lime cannot be positively shown to be connected with the previous operation of living beings, there is room for doubt whether this salt is not in reality always primarily a product of vital action. ‘The phosphatic nodules of the Upper Green- sand are erroneously called “coprolites,” from the belief originally entertained that they were the droppings or fossilised excrements of extinct animals; and though this is not the case, there can be little doubt but that the phosphate of lime which they contain is in this instance of organic origin.* It appears, in fact, that decaying animal matter has a singular power of determining the precipitation around it of mineral salts dis- solved in water. Thus, when any animal bodies are undergo- ing decay at the bottom of the sea, they have a tendency to cause the precipitation from the surrounding water of any mineral matters which may be dissolved in it ; and the organic body thus becomes a centre round which the mineral matters in question are deposited in the form of a “concretion” or “nodule.” The phosphatic nodules in question were formed in a sea in which phosphate of lime, derived from the destruc- tion of animal skeletons, was held largely in solution ; and a precipitation of it took place round any body, such as a decay- ing animal substance, which happened to be lying on the sea- bottom, and which offered itself as a favourable nucleus. In the same way we may explain the formation of the calcareous nodules, known as “septaria” or ‘‘cement stones,” which occur so commonly in the London Clay and Kimmeridge Clay, and in which the principal ingredient is carbonate of lime. A similar origin is to be ascribed to the nodules of clay iron-stone (impure carbonate of iron) which occur so abundantly in the shales of the Carboniferous series and in other argillaceous deposits ; and a parallel modern example is to be found in the nodules of manganese, which were found by Sir Wyville Thomson, in the Challenger, to be so numer- ously scattered over the floor of the Pacific at great depths. In accordance with this mode of origin, it is exceedingly common to find in the centre of all these nodules, both old and new, some organic body, such as a bone, a shell, or a tooth, which acted as the original nucleus of precipitation, and * It has been maintained, indeed, that the phosphatic nodules so largely worked for agricultural purposes, are in themselves actual organic bodies or true fossils. In a few cases this admits of demonstration, as it can be shown that the nodule is simply an organism (such as a sponge) infiltrated with phosphate of lime (Sollas) ; but there are many other cases in which no actual structure has yet been shown to exist, and as to the true origin of which it would be hazardous to offer a positive opinion. 32 PRINCIPLES OF PALZONTOLOGY. was thus preserved in a shroud of mineral matter. Many nodules, it is true, show no such nucleus; but it has been affirmed that all of them can be shown, by appropriate microscopical investigation, to have been formed round an original organic body to begin with (Hawkins Johnson). The last lime-salt which need be mentioned is gypsum, or sulphate of lime. This substance, apart from other modes of occurrence, is not uncommonly found interstratified with the ordinary sedimentary rocks, in the form of more or less irregu- lar beds; and in these cases it has a paleontological import- ance, as occasionally yielding well-preserved fossils. Whilst its exact mode of origin is uncertain, it cannot be regarded as in itself an organic rock, though clearly the product of chemical action. ‘To look at, it is usually a whitish or yellowish-white rock, as coarsely crystalline as loaf-sugar, or more so; and the microscope shows it to be composed entirely of crystals of sulphate of lime. We have seen that the calcareous or lime-containing rocks are the most important of the group of organic deposits; whilst the sz/iceous or flint-containing rocks may be regarded as the most important, most typical, and most generally distributed of the mechanically-formed rocks. We have, however, now briefly to consider certain deposits which are more or less completely formed of flint ; but which, nevertheless, are essen- tially organic in their origin. Flint or silex, hard and intractable as it is, is nevertheless capable of solution in water to a certain extent, and even of assuming, under certain circumstances, a gelatinous or viscous condition. Hence, some hot-springs are impregnated with silica to a considerable extent ; it is present in small quantity in sea-water; and there is reason to believe that a minute pro- portion must very generally be present in all bodies of fresh water as well. It is from this silica dissolved in the water that many animals and some plants are enabled to construct for themselves flinty skeletons; and we find that these animals and plants are and have been sufficiently numerous to give rise to very considerable deposits of siliceous matter by the mere accumulation of their skeletons. Amongst the animals which require special mention in this connection are the microscopic organisms which are known to the naturalist as Polycystina. These little creatures are of the lowest possible grade of organ- isation, very closely related to the animals which we have pre- viously spoken of as Foraminifera, but differing in the fact that they secrete a shell or skeleton composed of flint instead of lime. The Polycystina occur abundantly in our present seas ; THE FOSSILIFEROUS ROCKS. 33 and their shells are present in some numbers in the ooze which is found at great depths in the Atlantic and Pacific oceans, being easily recognised by their exquisite shape, their glassy transparency, the general presence of longer or shorter spines, and the sieve-like perforations in the walls. Both in Barbadoes and in the Nicobar islands occur geological formations which are composed of the flinty skeletons of these microscopic animals; the deposit in the former locality attaining a great thickness, and having been long known to workers with the microscope under the name of “ Barbadoes earth” (fig. 15). In addition to flint- producing animals, we have also the great group of fresh-water and marine microscopic plants Fig. 15.— Shells of Polycystina from Fig. 16.—Cases of Diatoms in the Rich- ‘*Barbadoes earth;” greatly magnified. mond ‘‘Infusorial earth;” highly magni- (Original.) fied. (Original.) known as Diatoms, which likewise secrete a siliceous skeleton, often of great beauty. The skeletons of Diatoms are found abundantly at the present day in lake-deposits, guano, the silt of estuaries, and in the mud which covers many parts of the sea-bottom ; they have been detected in strata of great age; .and in spite of their microscopic dimensions, they have not un- commonly accumulated to form deposits of great thickness, and of considerable superficial extent. Thus the celebrated deposit of ‘tripoli” (“ Polir-schiefer”) of Bohemia, largely worked as polishing-powder, is composed wholly, or almost wholly, of the flinty cases of Diatoms, of which it is calculated that no less than forty-one thousand millions go to make up a single cubic inch of the stone.. Another celebrated deposit is the so-called “Infusorial earth” of Richmond in Virginia, where there is a stratum in places thirty feet thick, composed almost entirely of the microscopic shells of Diatoms. Nodules or layers of fmf, or the impure variety of flint fe 34. PRINCIPLES OF PALAONTOLOGY. known as chert, are found in limestones of almost all ages from the Silurian upwards; but they are especially abundant in the chalk. When these flints are examined in thin and trans- parent slices under the microscope, or in polished sections, they are found to contain an abundance of minute organic bodies—such as Foraminifera, sponge-spicules, &c.—embedded in a siliceous basis. In many instances the flint contains larger organisms—such as a Sponge or a Sea-urchin: As the flint has completely surrounded and infiltrated the fossils which it contains, it is obvious that it must have been deposited from sea-water in a gelatinous condition, and subsequently have hardened. ‘That silica is capable of assuming this viscous and soluble condition is known; and the formation of flint may therefore be regarded as due to the separation of silica from the sea-water and its deposition round some organic body in a state of chemical change or decay, just as nodules of phos- phate of lime or carbonate of iron are produced. ‘The exist- ence of numerous organic bodies in flint has long been known; but it should be added that a recent observer (Mr Hawkins Johnson) asserts that the existence of an organic structure can be demonstrated by suitable methods of treatment, even in the actual matrix or basis of the flint.* In addition to deposits formed of flint itself, there are other siliceous deposits formed by certain szccates, and also of organic origin. It has been shown, namely—by observations carried out in our present seas—that the shells of Aoraminzfera are liable to become completely infiltrated by silicates (such as ‘‘ glauconite,” or silicate of iron and potash). Should the actual calcareous shell become dissolved away subsequent to this infiltration—as is also liable to occur—then, in place of the shells of the Foraminifera, we get a corresponding number of green sandy grains of glauconite, each grain being the cast of a single shell. It has thus been shown that the green sand found covering the sea-bottom in certain localities (as found by the Challenger expedition along the line of the Agulhas current) is really organic, and is composed of casts of the shells of Foraminifera. Long before these observations had been made, it had been shown by Professor Ehrenberg that the green sands of various geological formations are composed mainly of the internal casts of the shells of Foraminifera ; and * It has been asserted that the flints of the chalk are merely fossil sponges. No explanation of the origin of flint, however, can be satisfac- tory, unless it embraces the origin of chert in almost all great limestones from the Silurian upwards, as well as the common phenomenon of the silicification of organic bodies (such as corals and shells) which are known with certainty to have been originally calcareous. THE FOSSILIFEROUS ROCKS. 36 we have thus another and a very interesting example how rock- deposits of considerable extent and of geological importance can be built up by the operation of the minutest living beings. As regards argillaceous deposits, containing alumina or clay as their essential ingredient, it cannot be said that any of these have been actually shown to be of organic origin. A recent observation by Sir Wyville Thomson would, however, render it not improbable that some of the great argillaceous accumulations of past geological periods may be really organic. This distinguished observer, during the cruise of the Chal- lenger, showed that the calcareous ooze which has_ been already spoken of as covering large areas of the floor of the Atlantic and Pacific at great depths, and which consists almost wholly of the shells of Foraminifera, gave place at still greater depths to a red ooze consisting of impalpable clayey mud, coloured by oxide of iron, and devoid of traces of organic bodies. As the existence of this widely-diffused red ooze, in mid-ocean, and at such great depths, cannot be explained on the supposition that it is a sediment brought down into the sea by rivers, Sir Wyville Thomson came to the conclusion that it was probably formed by the action of the sea-water upon the shells of Foraminifera. These shells, though mainly consisting of lime, also contain a certain proportion of alumina, the former being soluble in the carbonic acid dissolved in the sea-water, whilst the latter is insoluble. There would further appear to be grounds for believing that the solvent power of the sea-water over lime is considerably increased at great depths. If, therefore, we suppose the shells of Foraminifera to be in course of deposition over the floor of the Pacific, at certain depths they would remain unchanged, and would ac- cumulate to form a calcareous ooze; but at greater depths they would be acted upon by the water, their lime would be dis- solved out, their form would disappear, and we should simply have left the small amount of alumina which they previously contained. In process of time this alumina would accumulate to form a bed of clay; and as this clay had been directly derived from the decomposition of the shells of animals, it would be fairly entitled to be considered an organic deposit. Though not finally established, the hypothesis of Sir Wyville Thomson on this subject is of the greatest interest to the pale- ontologist, as possibly serving to explain the occurrence, espe- cially in the older formations, of great deposits of argillaceous matter which are entirely destitute of traces of life. It only remains, in this connection, to shortly consider the rock-deposits in which carbo is found to be present in greater 36 PRINCIPLES OF PALAZONTOLOGY. or less quantity. In the great majority of cases where rocks are found to contain carbon or carbonaceous matter, it can be stated with certainty that this substance is of organic origin, though it is not necessarily derived from vegetables. Carbon derived from the decomposition of animal bodies is not uncom- mon; though it never occurs in such quantity from this source as it may do when it is derived from plants. Thus, many limestones are more or less highiy bituminous ; the celebrated siliceous flags or so-called “ bituminous schists” of Caithness are impregnated with oily matter apparently derived’ from the decomposition of the numerous fishes embedded in them; Silurian shales containing Graptolites, but destitute of plants, are not uncommonly “anthracitic,” and contain a small per- centage of carbon derived from the decay of these zoophytes ; whilst the petroleum so largely worked in North America has not improbably an animal origin. That the fatty compounds present in animal bodies should more or less extensively im- pregnate fossiliferous rock-masses, is only what might be ex- pected ; but the great bulk of the carbon which exists stored up in the earth’s crust is derived from plants ; and the form in which it principally presents itself is that of coal. We shall have to speak again, and at greater length, of coal, and it is sufficient to say here that all the true coals, anthracites, and lignites, are of organic origin, and consist principally of the remains of plants in a more or less altered condition. The bituminous shales which are found so commonly associated with beds of coal also derive their carbon primarily from plants ; and the same is certainly, or probably, the case with similar shales which are known to occur in formations younger than the Carboniferous. Lastly, carbon may occur as a con- spicuous constituent of rock-masses in the form of graphite or black-lead. In this form, it occurs in the shape of detached scales, of veins or strings, or sometimes of regular layers ;* and there can be little doubt that in many instances it has an organic origin, though this is not capable of direct proof. When present, at any rate, in quantity, and in the form of layers associated with stratified rocks, as is often the case in the Lau- rentian formation, there can be little hesitation in regarding it as of vegetable origin, and as an altered coal. * In the Huronian formation at Steel River, on the north shore of Lake Superior, there exists a bed of carbonaceous matter which is regularly in- terstratified with the surrounding rocks, and has a thickness of from 30 to 40 feet. This bed is shown by chemical analysis to contain about 50 per cent of carbon, partly in the form of graphite, partly in the form of anthra- cite ; and there can be little doubt but that it is really a stratum of ‘‘meta- morphic ” coal. CHRONOLOGICAL SUCCESSION. 37 GHA PTE R4E8E CHRONOLOGICAL SUCCESSION OF THE FOSSITIFE ROO S: ‘ROCESS. The physical geologist, who deals with rocks simply as rocks, and who does not necessarily trouble himself about what fossils they may contain, finds that the stratified deposits which form so large a portion of the visible part of the earth’s crust are not promiscuously heaped together, but that they have a cer- tain definite arrangement. In each country that he examines, he finds that certain groups of strata lie above certain other groups ; and in comparing different countries with one another, he finds that, in the main, the same groups of rocks are always found in the same relative position to each other. It is pos- sible, therefore, for the physical geologist to arrange the known stratified rocks into a successive series of groups, or “ forma- tions,” having a certain definite order. The establishment of this physical order amongst the rocks introduces, however, at once the element of me, and the physical succession of the strata can be converted directly into a historical or chronologt- cal succession. This is obvious, when we reflect that any bed or set of beds of sedimentary origin is clearly and necessarily younger than all the strata upon which it rests, and older than all those by which it is surmounted. It is possible, then, by an appeal to the rocks alone, to de- termine in each country the general physical succession of the strata, and this “ stratigraphical” arrangement, when once de- termined, gives us the relative ages of the successive groups. The task, however, of the physical geologist in this matter is immensely lightened when he calls in paleontology to his aid, and studies the evidence of the fossils embedded in the rocks. Not only is it thus much easier to determine the order of suc- cession of the strata in any given region, but it becomes now for the first time possible to compare, with certainty and pre- cision, the order of succession in one region with that which exists in other regions far distant. The value of fossils as tests of the relative ages of the sedimentary rocks depends on the fact that they are not indefinitely or promiscuously scattered through the crust of the earth,—as it is conceivable that they might be. On the contrary, the first and most firmly estab- lished law of Palzeontology is, that particular kinds of fossils 38 PRINCIPLES OF PALAZZONTOLOGY. are confined to particular rocks, and particular groups of fossils are confined to particular groups of rocks. Fossils, then, are distinctive of the rocks in which they are found—much more distinctive, in fact, than the mere mineral character of the rock can be, for “at commonly changes as a formation is traced from one region to another, whilst the fossils remain unaltered. It would therefore be quite possible for the paleontologist, by an appeal to the fossils alone, to arrange the series of sedi- mentary deposits into a pile of strata having a certain definite order. Not only would this be possible, but it would be found —if sufficient knowledge had been brought to bear on both sides—that the paleontological arrangement of the strata would coincide in its details with the stratigraphical or physical arrangement. Happily for science, there is no such division between the paleontologist and the physical geologist as here supposed ; but by the combined researches of the two, it has been found possible to divide the entire series of stratified deposits into a number of definite vock- groups or formations, which have a recognised order of succession, and each of which is charac- terised by possessing an assemblage of organic remains which do not occur in association in any other formation. Such an assemblage of fossils, characteristic of any given formation, re- presents the fe of the particular pevzod in which the formation was deposited. In this way the past history of the earth becomes divided into a series of successive /éfe-periods, each of which corresponds with the deposition of a particular forma- tion or group of strata. Whilst particular assemblages of organic forms characterise particular groups of rocks, it may be further said that, in a general way, each subdivision of each formation has its own peculiar fossils, by which it may be recognised by a skilled worker in Paleontology. Whenever, for instance, we meet with examples of the fossils which are known as Graffolites, we may be sure that we are dealing with Sc/wrian rocks (leaving out of sight one ortwo forms doubtfully referred to this family). We may, however, go much farther than this with perfect safety. If the Graptolites belong to certain genera, we may be quite certain that we are dealing with Zower Silurian rocks. Furthermore, if certain special forms are present, we may be even able to say to what exact subdivision of the Lower Silu- rian series they belong. As regards particular fossils, however, or even particular classes of fossils, conclusions of this nature require to be accom- panied by a tacit but well-understood reservation. So far as CHRONOLOGICAL SUCCESSION. 39 our present observation goes, none of the undoubted Grapto- lites have ever been discovered in rocks later than those known upon other grounds to be Silurian ; but it is possible that they might at any time be detected in younger deposits. Similarly, the species and genera which we now regard as characteristic of the Lower Silurian, may at some future time be found to have survived into the Upper Silurian period. We should not forget, therefore, in determining the age of strata by palzeonto- logical evidence, that we are always reasoning upon generalisa- tions which are the result of experience alone, and which are liable to be vitiated by further and additional discoveries. When the paleontological evidence as to the age of any given set of strata is corroborated by the physical evidence, our conclusions may be regarded as almost certain ; but there are certain limitations and fallacies in the palzeontological method of inquiry which deserve a passing mention. In the first place, fossils are not always present in the stratified rocks; many aqueous rocks are unfossiliferous, through a thickness of hundreds or even thousands of feet of little-altered sediments ; and even amongst beds which do contain fossils, we often meet with strata of many feet or yards in thickness which are wholly destitute of any traces of fossils. There are, therefore, to begin with, many cases in which there is no paleontological evidence extant or available as to the age of a given group of strata. In the second place, palzontological observers in different parts of the world are lable to give different names to the same fossil, and in all parts of the world they are occa- sionally liable to group together different fossils under the same title. Both these sources of fallacy require to be guarded against in reasoning as to the age of strata from their fossil remains. ‘Thirdly, the mere fact of fossils being found in beds which are known by physical evidence to be of different ages, has commonly led paleontologists to describe them as dif- ferent species. Thus, the same fossil, occurring in successive groups of strata, and with the merely trivial and varietal differ- ences due to the gradual change in its environment, has been repeatedly described as a distinct species, with a distinct name, in every bed in which it was found. We know, however, that many fossils range vertically through many groups of strata, and there are some which even pass through several forma- tions. The mere fact of a difference of physical position ought never to be taken into account at all in considering and determining the true affinities of a fossil. Fourthly, the results of experience, instead of being an assistance, are some- times liable to operate as a source of error. When once, 40 PRINCIPLES OF PALAZZSONTOLOGY. namely, a generalisation has been established that certain fossils occur in strata of a certain age, paleeontologists are apt to infer that a beds containing similar fossils must be of the same age. There is a presumption, of course, that this infer- ence would be correct; but it is not a conclusion resting upon absolute necessity, and there might be physical evidence to disprove it. Fifthly, the physical geologist may lead the palez- ontologist astray by asserting that the physical evidence as to the age and position of a given group of beds is clear and un- equivocal, when such evidence may be, in reality, very slight and doubtful. In this way, the observer may be readily led into wrong conclusions as to the nature of the organic remains —often obscure and fragmentary—which it is his business to examine, or he may be led erroneously to think that previous generalisations as to the age of certain kinds of fossils are premature and incorrect. Lastly, there are cases in which, owing to the limited exposure of the beds, to their being merely of local development, or to other causes, the physical evidence as to the age of a given group of strata may be en- tirely uncertain and unreliable, and in which, therefore, the observer has to rely wholly upon the fossils which he may meet with. In spite of the above limitations and fallacies, there can be no doubt as to the enormous value of palzontology in enab- ling us to work out the historical succession of the sedimentary rocks. It may even be said that in any case where there should appear to be a clear and decisive discordance between the physical and the paleontological evidence as to the age of a given series of beds, it is the former that is to be distrusted rather than the latter. The records of geological science con- tain not a few cases in which apparently clear physical evi- dence of superposition has been demonstrated to have been wrongly interpreted ; but the evidence of palzeontology, when in any way sufficient, has rarely been upset by subsequent investigations. Should we find strata containing plants of the Coal-measures apparently resting upon other strata with Am- monites and Belemnites, we may be sure that the physical evidence is delusive ; and though the above is an extreme case, the presumption in all such instances is rather that the physical succession has been misunderstood or misconstrued, than that there has been a subversion of the recognised succession of life-forms. We have seen, then, that as the collective result of observa- tions made upon the superposition of rocks in different locali- ties, from their mineral characters, and from their included CHRONOLOGICAL SUCCESSION. 4I fossils, geologists have been able to divide the entire stratified series into a number of different divisions or formations, each characterised by a gezera/ uniformity of mineral composition, and by a special and peculiar assemblage of organic forms. Each of these primary groups is in turn divided into a series of smaller divisions, characterised and distinguished in the same way. It is not pretended for a moment that all these primary rock-groups can anywhere be seen surmounting one another regularly.* There is no region upon the earth where all the stratified formations can be seen together; and, even when most of them occur in the same country, they can nowhere be seen all succeeding each other in their regular and uninterrupted succession. The reason of this is obvious. There are many places—to take a single example—where one may see the the Silurian rocks, the Devonian, and the Carbon- iferous rocks succeeding one another regularly, and in their proper order. This is because the particular region where this occurs was always submerged beneath the sea while these for- mations were being deposited. There are, however, many more localities in which one would find the Carboniferous rocks resting unconformably upon the Silurians without the intervention of any strata which could be referred to the Devonian period. This might arise from one of two causes: 1. The Silurians might have been elevated above the sea im- mediately after their deposition, so as to form dry land during the whole of the Devonian period, in which case, of course, no strata of the latter age could possibly be deposited in that area. 2. The Devonian might have been deposited upon the Silurian, and then the whole might have been elevated above the sea, and subjected to an amount of denudation sufficient to remove the Devonian strata entirely. In this case, when the land was again submerged, the Carboniferous rocks, or any younger formation, might be deposited directly upon Silurian strata. From one or other of these causes, then, or from subse- quent disturbances and denudations, it happens that we can * As we have every reason to believe that dry land and sea have existed, at any rate from the commencement of the Laurentian period to the present day, it is quite obvious that no one of the great formations can ever, under any cir- cumstances, have extended over the entire globe. In other words, no one of the formations can ever have had a greater geographical extent than that of the seas of the period in which the formation was deposited. Nor is there any reason for thinking that the proportion of dry land to ocean has ever been materially different to what it is at present, however greatly the areas of sea and land may have changed as regards their place. It follows from the above, that there is no sufficient basis for the view that the crust of the earth is com- posed of a succession of concentric layers, like the coats of an onion, each layer representing one formation. 42 PRINCIPLES OF PALAZZONTOLOGY. rarely find many of the primary formations following one another consecutively and in their regular order. In no case, however, do we ever find the Devonian resting upon the Carboniferous, or the Silurian rocks reposing on the Devonian. We have therefore, by a comparison of many different areas, an established order of succession of the strati- fied formations, as shown in the subjoined ideal section of the crust of the earth (fig. 17). The main subdivisions of the stratified rocks are known by the following names :— 1. Laurentian. 2. Cambrian (with Huronian ?). 3. Silurian. 4. Devonian or Old Red Sandstone. 5. Carboniferous. Oats ae LN ew Red Sandstone. 7. Triassic 8. Jurassic or Oolitic. g. Cretaceous. 1o. Eocene. 11. Miocene. 2. Phocene: 13. Post-tertiary. KAINOZOIC. MESOZOIC. PALAZOZOIC. CHRONOLOGICAL SUCCESSION. A3 IDEAL SECTION OF THE CRUST OF THE EARTH. Fig. 17. Yo Post-tertiary and Recent. |} Pliocene. Eocene. —— == Cretaceous. Oolitic or Jurassic. Triassic. Ce ee Permian. Carboniferous. Devonian or Old Red Sandstone. = =|. , | ° 4400002900550 Om) (9) 0' co Cambrian. Huronian. Laurentian. 44 PRINCIPLES OF PALAZZONTOLOGY. Of these primary rock divisions, the Laurentian, Cambrian, Silurian, Devonian, Carboniferous, and Permian are collec- tively grouped together under the name of the Avzmary or Paleozoic rocks (Gr. palaios, ancient; zoe, life). Not only do they constitute the oldest stratified accumulations, but from the extreme divergence between their animals and plants and those now in existence, they may appropriately be considered as belonging to an “ Old-Life” period of the world’s history. The Triassic, Jurassic, and Cretaceous systems are grouped to- gether as the Secondary or Afesozoic formations (Gr. mesos, inter- mediate ; oe, life); the organic remains of this ‘“‘ Middle-Life ” period being, on the whole, intermediate in their characters between those of the palzozoic epoch and those of more modern strata. Lastly, the Eocene, Miocene, and Pliocene formations are grouped together as the Zértiary or Kaznozoic rocks (Gr. ainos, new; zoe, life); because they constitute a “* New-Life” period, in which the organic remains approximate in character to those now existing upon the globe. ‘The so- called Post-Tertzary deposits are placed with the Kainozoic, or may be considered as forming a separate Quaternary system. CHAPTER Me Let OR thas i ane ita td yyerk eed) PATLCS 7 ; 3 ’ fh Sy " y BEEMAN Rai He i rie Le Tejhy) ee le hy UAE eh; ‘ae ithe Let es ue, PRO ee gaat a(t) 3 eer © ae ‘ sitters! ‘ a ay ‘ ‘ 4 a ey Mae gt pd Se Has FORICAL...PAE ALON TOLOGY: Puke Rob ee CHA PT ERS NATE THE LAURENTIAN AND HURONIAN PERIODS. THE Laurentian Rocks constitute the base of the entire strati- fied series, and are, therefore, the oldest sediments of which we have as yet any knowledge. ‘They are more largely and more typically developed in North America, and especially in Canada, than in any known part of the world, and they derive their title from the range of hills which the old French geo- graphers named the “Laurentides.” These hills are com- posed of Laurentian Rocks, and form the watershed between the valley of the St Lawrence river on the one hand, and the great plains which stretch northwards to Hudson Bay on the other hand. The main area of these ancient deposits forms a great belt of rugged and undulating country, which extends from Labrador westwards to Lake Superior, and then bends northwards towards the Arctic Sea. Throughout this extensive area the Laurentian Rocks for the most part present themselves in the form of low, rounded, ice-worn hills, which, if generally wanting in actual sublimity, have a certain geological grandeur from the fact that they “Shave endured the battles and the storms of time longer than any other mountains” (Dawson). In some places, however, the Laurentian Rocks produce scenery of the most magnificent character, as in the great gorge cut through them by the river Saguenay, where they rise at times into ver- tical precipices 1500 feet in height. In the famous group of the Adirondack mountains, also, in the state of New York, they form elevations no less than 6000 feet above the level of the sea. As a general rule, the character of the Laurentian region is that of a rugged, rocky, rolling country, often densely E 66 HISTORICAL PAL/ZEONTOLOGY. timbered, but rarely well fitted for agriculture, and chiefly attractive to the hunter and the miner. As regards its mineral characters, the Laurentian series 1s composed throughout of metamorphic and highly crystalline rocks, which are in a high degree crumpled, folded, and faulted. By the late Sir William Logan the entire series was divided into two great groups, the Lower Laurentian and the Upper Laurentian, of which the latter rests unconformably upon the truncated edges of the former, and is in turn uncon- formably overlaid by strata of Huronian and Cambrian age (fig. 20). The Lower Laurentian series attains the enormous thickness of Fig. 20.—Diagrammatic section of thé Laurentian Rocks in Lower Canada. a@ Lower Laurentian; 4 Upper Laurentian, resting unconformably upon the lower series; c Cam- brian strata (Potsdam Sandstone), resting unconformably on the Upper Laurrentian. over 20,000 feet, and is composed mainly of great beds of gneiss, altered sandstones (quartzites), mica-schist, hornblende-schist, magnetic iron-ore, and hzmatite, together with masses of lime- stone. ‘The limestones are especially interesting, and have an extraordinary development—three principal beds being known, of which one is not less than 1500 feet thick ; the collective thickness of the whole being about 3500 feet. The Upper Laurentian series, as before said, reposes uncon- formably upon the Lower Laurentian, and attains a thickness of at least 10,000 feet. Like the preceding, it is wholly meta- morphic, and 1s composed partly of masses of gneiss and quartz- ite ; but it is especially distinguished by the possession of great beds of felspathic rock, consisting principally of ‘ Labrador felspar.”’ Though typically developed in the great Canadian area already spoken of, the Laurentian Rocks occur in other locali- ties, both in America and in the Old World. In Britain, the so-called ‘fundamental gneiss” of the Hebrides and of Suther- landshire is probably of Lower Laurentian age, and the “ hy- persthene rocks” of the Isle of Skye may, with great proba- bility, be regarded as referable to the Upper Laurentian. In other localities in Great Britain (as in St David’s, South Wales ; the Malvern Hills; and the North of Ireland) occur ancient metamorphic deposits which also are probably refer- able to the Laurentian series. The so-called “ primitive gneiss” of Norway appears to belong to the Laurentian, and the THE LAURENTIAN AND HURONIAN PERIODS. 67 ancient metamorphic rocks of Bohemia and Bavaria may be regarded as being approximately of the same age. By some geological writers the ancient and highly meta- morphosed sediments of the Laurentian and the succeeding Huronian series have been spoken of as the “ Azoic rocks” (Gr. a, without ; zoe, life) ; but even if we were wholly destitute of any evidence of life during these periods, this name would be objectionable upon theoretical grounds. Ifa general name be needed, that of ‘ Eozoic” (Gr. eos, dawn ; zoe, life), proposed by Principal Dawson, is the most appropriate. Owing to their metamorphic condition, geologists long despaired of ever de- tecting any traces of life in the vast pile of strata which con- stitute the Laurentian System. Even before any direct traces were discovered, it was, however, pointed out that there were good reasons for believing that the Laurentian seas had been tenanted by an abundance of living beings. These reasons are briefly as follows :—(1) Firstly, the Laurentian series con- sists, beyond question, of marine sediments which originally differed in no essential respect from those which were subse- quently laid down in the Cambrian or Silurian periods. (2) In all formations later than the Laurentian, any limestones which are present can be shown, with few exceptions, to be organic rocks, and to be more or less largely made up of the comminuted debris of marine or fresh-water animals. The Laurentian limestones, in consequence of the metamorphism to which they have been subjected, are so highly crystalline (fig. 21) that the microscope fails to detect any organic struc- ture in the rock, and no fos- sils beyond those which will be spoken of immediately have as yet been discovered in them. We know, however, of numerous cases in which lime- stones, of later age, and un- doubtedly organic to begin with, have been rendered so intensely crystalline by meta- morphic action that all traces of organic structure have been ? obliterated. We have there- eZ fore, by analogy, the strongest __ Fig. 21.—Section of Lower Laurentian possible ground for believing Fingone from Hull, Ottawa; enlarged that the vast beds of Lauren- crystalline, and contains mica and other tian limestone have been ori- ea eeittal Only acne ginally organic in their origin, and primitively composed, in the main, of the calcareous skele- 68 HISTORICAL PALAZONTOLOGY. tons of marine animals. It would, in fact, be a matter of great difficulty to account for the formation of these great cal- careous masses on any other hypothesis. (3) The occurrence of phosphate of lime in the Laurentian Rocks in great abundance, and sometimes in the form of irregular beds, may very possibly be connected with the former existence in the strata of the re- mains of marine animals of whose skeleton this mineral is a con- stituent. (4) The Laurentian Rocks contain a vast amount of carbon in the form of black-lead or graphite. ‘This mineral is especially abundant in the limestones, occurring in regular beds, in veins or strings, or disseminated through the body of the lime- stone in the shape of crystals, scales, or irregular masses. The amount of graphite in some parts of the Lower Laurentian is so great that it has been calculated as equal to the quantity of carbon present in an equal thickness of the Coal-measures. The general source of solid carbon in the crust of the earth is, however, plant-life ; and it seems impossible to account for the Laurentian graphite, except upon the supposition that it is metamorphosed vegetable matter. (5) Lastly, the great beds of iron-ore (peroxide and magnetic oxide) which occur in the Laurentian series interstratified with the other rocks, point with great probability to the action of vegetable life; since similar deposits in later formations can commonly be shown to have been formed by the deoxidising power of vege- table matter in a state of decay. In the words of Principal Dawson, ‘any one of these rea- sons might, in itself, be held insufficient to prove so great and, at first sight, unlikely a conclusion as that of the existence of abundant animal and vegetable life in the Laurentian; but the concurrence of the whole in a series of deposits unquestion- ably marine, forms a chain of evidence so powerful that it might command belief even if no fragment of any organic or living form or structure had ever been recognised in these an- cient rocks.” Of late years, however, there have been dis- covered in the Laurentian Rocks certain bodies which are believed to be truly the remains of animals, and of which by far the most important is the structure known under the now celebrated name of Zozodn. If truly organic, a very special and exceptional interest attaches itself to Hozodn, as being the most ancient fossil animal of which we have any knowledge ; but there are some who regard it really a peculiar form of mineral structure, and a severe, protracted, and still unfinished controversy has been carried on as to its nature. Into this controversy it is wholly unnecessary to enter here ; and it will be sufficient to briefly explain the structure of Hozodn, as eluci- dated by the elaborate and masterly investigations of Car- THE LAURENTIAN AND HURONIAN PERIODS. 69 penter and Dawson, from the standpoint that it is a genuine organism—the balance of evidence up to this moment inclin- ing decisively to this view. The structure known as £ozoon is found in various localities in the Lower Laurentian limestones of Canada, in the form of isolated masses or spreading layers, which are composed of thin alternating laminz, arranged more or less concentrically (fig. 22). The laminz of these masses are usually of different Fig. 22.—Fragment of Eozoén, of the natural size, showing alternate lamine of loganite and dolomite. (After Dawson.) colours and composition ; one series being white, and com- posed of carbonate of lime—whilst the lamine of the second series alternate with the preceding, are green in colour, and are found by chemical analysis to consist of some silicate, generally serpentine or the closely-related “‘loganite.” In some instances, however, all the laminz are calcareous, the concentric arrangement still remaining visible in consequence of the fact that the Jaminz are composed alternately of lighter and darker coloured limestone. When first discovered, the masses of Lozodn were supposed to be of a mineral nature; but their striking general resem- blance to the undoubted fossils which will be subsequently spoken of under the name of Stromatopora was recognised by Sir William Logan, and specimens were submitted for minute examination, first to Principal Dawson, and subsequently to Die WizB. Carpenter. After a careful microscopic examina- tion, these two distinguished observers came to the conclusion that Lozodn was truly organic, and in this opinion they were afterwards corroborated by other high authorities (Mr W. K. Parker, Profesor Rupert Jones, Mr H. B. Brady, Professor Giimbel, &c.) Stated briefly, the structure of Hozodn, as ex- hibited by the microscope, is as follows :— 70 HISTORICAL PALAONTOLOGY. The concentrically-laminated mass of £ozodz is composed of numerous calcareous layers, representing the original skele- ton of the organism (fig. 23, 4). ‘These calcareous layers serve to separate and de- fine a series of cham- bers arranged in suc- cessive tiers, one above the other (fig. 23, A, 3B @ietae they are perforated not only by passages (fig. 23, <2) vcwmien Hy / py serve to place suc- ae i cessive tiers of cham- bers in communica- yrrurys yoru “ tion, but also by a YM ~ : a a system of delicate Fig. 23.—Diagram of a portion of Zozodz cut-verti- branching canals (fig. cally. A, B, C, Three tiers of chambers communicating with one another by slightly constricted apertures: @ a, 23) @). Moreover, The true shell-wall, perforated by numerous delicate the central and prin- tubes; 4 4, The main caleareous skeleton (‘‘intermedi- : : ate skeleton”); c, Passage of communication (“‘stolon- cipal portion of each passage fom one eof chambers another; Rami” calcareous layer, with penter.) the ramified canal- system just spoken of, is bounded both above and below by a thin lamina which has a structure of its own, and which may be regarded as the proper shell-wall (fig. 23,a@a@). This proper wall forms the actual lin- ing of the chambers, as well as the outer surface of the whole mass; and it is perforated with numerous fine vertical tubes (fig. 24, a a), opening into the chambers and on to the sur- face by corresponding fine pores. From the resemblance of this tubulated layer to similar structures in the shell of the Nummulite, it is often spoken of as the ‘“‘ Nummuline layer.” The chambers are sometimes piled up one above the other in an irregular manner; but they are more commonly arranged in regular tiers, the separate chambers being marked off from one another by projections of the wall in the form of parti- tions, which are so far imperfect as to allow of a free communi- cation between contiguous chambers. In the original condi- tion of the organism, all these chambers, of course, must have been filled with living matter; but they are found in the present state of the fossil to be generally filled with some silicate, such as serpentine, which not only fills the actual chambers, but has also penetrated the minute tubes of the proper wall and the branching canals of the intermediate skeleton. In some cases THE LAURENTIAN AND HURONIAN PERIODS. 7I the chambers are simply filled with crystalline carbonate of lime. When the originally porous fossil has been permeated BEA yy, ise A 4 fo Peg -Z Fiz. 24.—Portion of one of the calcareous layers of Hozod, magnified roo diameters. a a, The proper wall (“‘ Nummuline layer”) of one of the chambers, showing the fine ver- tical tubuli with which it is penetrated, and which are slightly bent along the line @’ a’. cc, The intermediate skeleton, with numerous branched canals. The oblique lines are the cleavage planes of the carbonate of lime, extending across both the intermediate skeleton and the proper wall. (After Carpenter.) by a silicate, it is possible to dissolve away the whole of the calcareous skeleton by means of acids, leaving an accurate and beautiful cast of the chambers and the tubes connected with them in the insoluble silicate. The above are the actual appearances presented by Lozoon when examined microscopically, and it remains to see how far they enable us to decide upon its true position in the animal kingdom. Those who wish to study this interesting subject in detail must consult the admirable memoirs by Dr W. B. Carpenter and Principal Dawson: it will be enough here to indicate the results which have been arrived at. The only. animals at the present day which possess a continuous calcareous skeleton, perforated by pores and penetrated by canals, are certain organisms belonging to the group of the Foraminifera. We have had occasion before to speak of these animals, and as they are not conspicuous or commonly-known forms of life, it may be well to say a few words as to the structure of the living representatives of the group. The Foraminifera are all inhabitants of the sea, and are mostly of small or even microscopic dimensions. . Their bodies are com- 72 HISTORICAL PALAZONTOLOGY. posed of an apparently structureless animal substance of an albuminous nature (“‘sarcode”), of a gelatinous consistence, transparent, and exhibiting numerous minute granules or rounded particles. The body-substance cannot be said in itself to possess any definite form, except in so far as it may be bounded by a shell; but it has the power, wherever it may be exposed, of emitting long thread-like filaments (‘ pseudo- podia”), which interlace with one another to form a network (fig. 25,0). These filaments can be thrown out at will, and [ Fig. 25.—The animal of Noxzonina, one of the Foraminifera, after the shell has been removed by a weak acid; 4, Gromweia, a single-chambered Foraminifer (after Schultze), showing the shell surrounded by a network of filaments derived from the body substance. to considerable distances, and can be again retracted into the soft mass of the general body-substance, and they are the agents by which the animal obtains its food. ‘The soft bodies of the oraminifera are protected by a shell, which is usually calcareous, but may be composed of sand-grains cemented THE LAURENTIAN AND HURONIAN PERIODS. 73 together ; and it may consist of a single chamber (fig. 26, a), or of many chambers arranged in different ways (fig. 26, -/). Fig. 26.—Shells of living Poramintfera. a, Orbulina universa, in its perfect condi- tion, showing the tubular spines which radiate from the surface of the shell; 4, Glod7- gerina bulloides, in its ordinary condition, the thin hollow spines which are attached to the shell when perfect having been broken off; c, Textudlaria variabilis; d, Peneroplis planatus; e, Rotalia concamerata; f, Cristellaria subarcuatula. (Fig. a@ is after baa Thomson; the others are after Williamson. All the figures are greatly en- arged.] Sometimes the shell has but one large opening into it—the mouth ; and then it is from this aperture that the animal pro- trudes the delicate net of filaments with which it seeks its food. In other cases the entire shell is perforated with minute pores (fig. 26, e), through which the soft body-substance gains the exterior, covering the whole shell with a gelatinous film of animal matter, from which filaments can be emitted at any point. When the shell consists of many chambers, all of these are placed in direct communication with one another, and the actual substance of the shell is often traversed by minute canals filled with living matter (¢g., in Calarina and Nummulina). ‘The shell, therefore, may be regarded, in such cases, asa more or less completely porous calcareous structure, 74 PRINCIPLES OF PALHONTOLOGY. filled to its minutest internal recesses with the substance of the living animal, and covered externally with a layer of the same substance, giving off a network of interlacing filaments. Such, in brief, is the structure of the living /oraminifera ; and it is believed that in Hozodz we have an extinct example of the same group, not only of special interest from its imme- morial antiquity, but hardly less striking from its gigantic dimensions. In its original condition, the entire chamber- system of “ozodn is believed to have been filled with soft structureless living matter, which passed from chamber to chamber through the wide apertures connecting these cavities, and from tier to tier by means of the tubuli in the shell-wall and the branching canals in the intermediate skeleton. Through the perforated shell-wall covering the outer surface the soft body-substance flowed out, forming a gelatinous investment, from every point of which radiated an interlacing net of deli- cate filaments, providing nourishment for the entire colony. In its present state, as before said, all the cavities originally occupied by the body-substance have been filled with some mineral substance, generally with one of the silicates of mag- nesia; and it has been asserted that this fact militates strongly against the organic nature of Lozodn, if not absolutely dis- proving it. As a matter of fact, however—as previously no- ticed—it is by no means very uncommon at the present day to find the shells of living species of Foraminifera in which all the cavities primitively occupied by the body-substance, down to the minutest pores and canals, have been similarly injected by some analogous silicate, such as glauconite. Those, then, whose opinions on such a subject deservedly carry the greatest weight, are decisively of opinion that we are presented in the Zozoon of the Laurentian Rocks of Canada with an ancient, colossal, and in some respects abnormal type of the Foraminifera. In the words of Dr Carpenter, it is not pretended that “‘the doctrine of the Foraminiferal nature of Lozoon can be proved in the demonstrative sense;” but it may be affirmed “that the convergence of a number of separate and independent probabilities, all accordant with that hypothesis, while a separate explanation must be invented for each of them on any other hypothesis, gives it that Aigh probability on which we rest in the ordinary affairs of life, in the verdicts of juries, and in the interpretation of geological phenomena generally.” It only remains to be added, that whilst Hozodn is by far the most important organic body hitherto found in the Lauren- tian, and has been here treated at proportionate length, other THE LAURENTIAN AND HURONIAN PERIODS. 75 traces of life have been detected, which may subsequently prove of great interest and importance. ‘Thus, Principal Dawson has recently described under the name of Archeo- spherine certain singular rounded bodies which he has dis- covered in the Laurentian limestones, and which he believes to be casts of the shells of Foraminifera possibly somewhat allied to the existing G/obigerine. ‘The same eminent palzeon- tologist has also described undoubted worm - burrows from rocks probably of Laurentian age. Further and more extend- ed researches, we may reasonably hope, will probably bring to light other actual remains of organisms in these ancient deposits. THE HURONIAN PERIOD. The so-called Muronian Rocks, like the Laurentian, have their typical development in Canada, and derive their name from the fact that they occupy an extensive area on the borders of Lake Huron. They are wholly metamorphic, and consist principally of altered sandstones or quartzites, siliceous, fels- pathic, or talcose slates, conglomerates, and limestones. They are largely developed on the north shore of Lake Superior, and give rise to a broken and hilly country, very like that occupied by the Laurentians, with an abundance of timber, but rarely with sufficient soil of good quality for agricultural purposes. They are, however, largely intersected by mineral veins, containing silver, gold, and other metals, and they will ultimately doubtless yield a rich harvest to the miner. The Huronian Rocks have been identified, with greater or less certainty, in other parts of North America, and also in the Old World. The total thickness of the Huronian Rocks in Canada is estimated as being not less than 18,000 feet, but there is con- siderable doubt as to their precise. geological position. In their typical area they rest unconformably on the edges of strata of Zower Laurentian age ; but they have never been seen in direct contact with the Uffer Laurentian, and their exact relations to this series are therefore doubtful. It is thus open to question whether the Huronian Rocks constitute a distinct formation, to be intercalated in point of time between the Laurentian and the Cambrian groups; or whether, rather, they should not be considered as the metamorphosed representa- tives of the Lower Cambrian Rocks of other regions. _ As regards the fossils of the Huronian Rocks, little can be said. Some of the specimens of Lozoon Canadense which have 70 HISTORICAL PALAZAONTOLOGY. been discovered in Canada are thought to come from rocks which are probably of Huronian age. In Bavaria, Dr Giimbel has described a species of Hozoon under the name of Fozodn Bavaricum, from certain metamorphic limestones which he refers to the Huronian formation. Lastly, the late Mr Billings described, from rocks in Newfoundland apparently referable to the Huronian, certain problematical limpet-shaped fossils, to which he gave the name of Asfzdel/a. LITERATURE. Amongst the works and memoirs which the student may consult with regard to the Laurentian and Huronian deposits may be mentioned the following :*— (1) ‘Report of Progress of the Geological Survey of Canada from its Commencement to 1863,’ pp. 38-49, and pp. 50-66. (2) ‘Manual of Geology.” Dana. 2d Ed. 1875. (3) ‘The Dawn of Life.’ J. W. Dawson. 1876. (4) ‘*On the Occurrence of Organic Remains in the Laurentian Rocks of Canada.” Sir W. E. Logan. ‘ Quart. Journ. Geol. Soc.,’ XX1. 45-50. (5) ‘*On the Structure of Certain Organic Remains in the Laurentian Limestones of Canada.” J. W. Dawson. ‘ Quart. Journ. Geol. Soc.,’ xxi. 51-59. (6) ‘* Additional Note on the Structure and Affinities of Eozoon Cana- dense.” W. B. Carpenter. ‘Quart. Journ. Geol. Soc.,’ xxi. (7) ‘‘Supplemental Notes on the Structure and Affinities of Eozoon Canadense.” W. B. Carpenter. ‘Quart. Journ. Geol. Soc.,’ Xxil, 219-228. (8) ‘*Onthe So-Called Eozodnal Rocks.” King & Rowney. ‘ Quart. Journ. Geol. Soc.,’ xxii. 185-218. (9) ‘Chemical and Geological Essays.’ Sterry Hunt. The above list only includes some of the more important memoirs which may be consulted as to the geological and chemical features of the Lauren- tian and Huronian Rocks, and as to the true nature of Zozodx. Those who are desirous of studying the later phases of the controversy with re- gard to Lozodu must consult the papers of Carpenter, Carter, Dawson, King & Rowney, Hahn, and others, in the ‘ Quart. Journ. of the Geological Society,’ the ‘ Proceedings of the Royal Irish Academy,’ the ‘ Annals of Nat- ural History,’ the ‘Geological Magazine,’ &c. Dr Carpenter’s ‘ Introduc- tion to the Study of the Foraminifera.’ should also be consulted. * Tn this and in all subsequently following bibliographical lists, not only is the selection of works and memoirs quoted necessarily extremely limited ; but only such have, asa general rule, been chosen for mention as are easily accessible to students who are in the position of being able to refer to a good library. Exceptions, however, are occasionally made to this rule, in favour of memoirs or works of special historical interest. It is also un- necessary to add that it has not been thought requisite to insert in these lists the well-known handbooks of geological and paleontological science, except in such instances as where they contain special information on special points. THE CAMBRIAN PERIOD. Th CHAPTER “Vile. THE CAMBRIAN PERIOD. The traces of life in the Laurentian period, as we have seen, are but scanty ; but the Cambrian Rocks—so called from their occurrence in North Wales and its borders (“‘ Cambria”)—have yielded numerous remains of animals and some dubious plants. The Cambrian deposits have thus a special interest as being the oldest rocks in which occur any number of well-preserved and unquestionable organisms. We have here the remains of the first fauna, or assemblage of animals, of which we have at present knowledge. As regards their geographical distribu- tion, the Cambrian Rocks have been recognised in many parts of the world, but there is some question as to the precise limits of the formation, and we may consider that their most typical area is in South Wales, where they have been carefully worked out, chiefly by Dr Henry Hicks. In this region, in the neigh- bourhood of the promontory of St David’s, the Cambrian Rocks are largely developed, resting upon an ancient ridge of Pre- Cambrian (Laurentian?) strata, and overlaid by the lowest beds of the Lower Silurian. ‘The subjoined sketch-section (fig. 27) exhibits in a general manner the succession of strata in this locality. From this section it will be seen that the Cambrian Rocks in Wales are divided in the first place into a lower and an upper group. The Zower Cambrian is constituted at the base by a great series of grits, sandstones, conglomerates, and slates, which are known as the “‘ Longmynd group,” from their vast development in the Longmynd Hills in Shropshire, and which attain in North Wales a thickness of 8000 feet or more. The Longmynd beds are succeeded by the so-called “‘ Mene- vian group,” a series of sandstones, flags, and grits, about 600 feet in thickness, and containing a considerable number of fossils. ‘The Upper Cambrian series consists in its lower por- tion of nearly 5000 feet of strata, principally shaly and slaty, which are known as the “Lingula Flags,” from the great abundance in them of a shell referable to the genus Zzzgu/a. These are followed by tooo feet of dark shales and flaggy sandstones, which are known as the “‘ Tremadoc slates,” from their occurrence near Tremadoc in North Wales ; and these in turn are surmounted, apparently quite conformably, by the basement beds of the Lower Silurian. 78 HISTORICAL PALAEONTOLOGY. GENERALISED SECTION OF THE CAMBRIAN ROCKS IN WALES. Arenig Group (Base of the Lower Silurian). Tremadoc Slates. 2 = Upper Lingula Flags. s) Heegte is Middle Lingula Flags. = | Lower Lingula Flags. Menevian Group. Z = ea q < ©) a Longmynd or Harlech Group. 3 -| Pre-Cambrian Rocks, The above may be regarded as giving a typical series of the Cambrian Rocks in a typical locality ; but strata of Cambrian age are known in many other regions, of which it is only possible here to allude to a few of the most important. In Scandinavia occurs a well-developed series of Cambrian de- posits, representing both the lower and upper parts of the THE CAMBRIAN PERIOD. 79 formation. In Bohemia, the Upper Cambrian, in particular, is largely developed, and constitutes the so-called “ Primordial zone” of Barrande. Lastly, in North America, whilst the Lower Cambrian is only imperfectly developed, or is repre- sented by the Huronian, the Upper Cambrian formation has a wide extension, containing fossils similar in character to the analogous strata in Europe, and known as the “ Potsdam Sand- stone.” The subjoined table shows the chief areas where Cam- brian Rocks are developed, and their general equivalency : TABULAR VIEW OF THE CAMBRIAN FORMATION. Britain. Lurofpe. America. a. Tremadoc Slates. | a. Primordialzone| a. Potsdam of Bohemia. Sandstone. 6, Lingula Flags. 6, Paradoxides 6. Acadian Upper Schists, Olenus group of New Cambrian. Schists, and Dict- Brunswick. yonema schists of Sweden. a. Longmynd Beds. | a. Fucoidal Sand- Huronian stone of Sweden. Formation ? 6. Llanberis Slates. | 0. Hophyton Sand- stone of Sweden. c. Harlech Grits. Lower ad. Oldhamia_ Slates Cambrian. of Ireland. e. Conglomerates and Sandstones of Sutherlandshire ? jf. Menevian Beds. | Like all the older Palzeozoic deposits, the Cambrian Rocks, though by no means necessarily what would be called actually ‘‘metamorphic,” have been highly cleaved, and otherwise altered from their original condition. Owing partly to their indurated state, and partly to their great antiquity, they are usually found in the heart of mountainous districts, which have © undergone great disturbance, and have been subjected to an enormous amount of denudation. In some cases, as in the Longmynd Hills in Shropshire, they form low rounded eleva- tions, largely covered by pasture, and with few or no elements of sublimity. In other cases, however, they rise into bold and rugged mountains, girded by precipitous cliffs. Industrially, the Cambrian Rocks are of interest, if only for the reason that the celebrated Welsh slates of Llanberis are derived from highly-cleaved beds of this age. ‘Taken as a whole, the Cam- brian formation is essentially composed of arenaceous and 80 HISTORICAL PALAZZONTOLOGY. muddy sediments, the latter being sometimes red, but more commonly nearly black in colour. It has often been supposed that the Cambrians are a deep-sea deposit, and that we may thus account for the few fossils contained in them; but the paucity of fossils is to a large extent imaginary, and some of the Lower Cambrian beds of the Longmynd Hills would ap- pear to have been laid down in shallow water, as they exhibit rain-prints, sun-cracks, and ripple-marks—incontrovertible evi- dence of their having been a shore-deposit. The occurrence of innumerable worm-tracks and burrows in many Cambrian strata is also a proof of shallow-water conditions ; and the gen- eral absence of limestones, coupled with the coarse mechani- cal nature of many of the sediments of the Lower Cambrian, may be taken as pointing in the same direction. The Zife of the Cambrian, though not so rich as in the suc- ceeding Silurian period, nevertheless consists of representa- tives of most of the great classes of invertebrate animals. ‘The coarse sandy deposits of the formation, which abound more particularly towards its lower part, naturally are to a large extent barren of fossils; but the muddy sediments, when not too highly cleaved, and especially towards the summit of the group, are replete with organicremains. ‘This is also the case, in many localities at any rate, with the finer beds of the Potsdam Sandstone in America. Limestones are known to occur in only a few areas (chiefly in America), and this may account for the apparent total absence of corals. It is, however, interest- ing to note that, with this exception, almost all the other lead- ing groups of Invertebrates are known to have come into existence during the Cambrian period. Of the land- surfaces of the Cambrian period we know nothing ; and there is, therefore, nothing surprising in the fact that our acquaintance with the Cambrian vegetation is confined to some marine plants or sea-weeds, often of a very obscure and problematical nature. The “ Fucoidal Sandstone” of Sweden, and the “ Potsdam Sandstone” of North America, have both yielded numerous remains which have been regarded as mark- ings left by sea-weeds or “ Fucoids ;” but these are highly enig- matical in their characters, and would, in many instances, seem to be rather referable to the tracks and burrows of marine worms. ‘The first-mentioned of these formations has also yielded the curious, furrowed and striated stems which have been described as a kind of land-plant under the name of Lophyton (fig. 28). It cannot be said, however, that the vege- table origin of these singular bodies has been satisfactorily proved. Lastly, there are found in certain green and purple THE CAMBRIAN PERIOD. SI beds of Lower Cambrian age at Bray Head, Wicklow, Ireland, some very remarkable fossils, which are well known under the XY INKY Y Xs AH SS ~ AA\S Fig. 28.—Fragment of Zophyton Linneanumt, a supposed land-plant, Lower Cambrian, Sweden, of the natural size. name of O/dhamia, but the true nature of which is very doubtful. The commonest form of O/dhamia (fig. 29) consists of a thread-like stem or axis, from which spring at regular intervals bundles of short filamentous branches in a fan-like manner. In the locality where it occurs, the fronds of O/dhamua are very abundant, and are spread over the surfaces of the strata in tangled layers. ‘That it is organic is certain, and that it is a calcareous sea-weed is probable ; but it may possibly belong to the sea-mosses (/olyzoa), or to the sea-firs (Sertudarians). Amongst the lower forms of animal life (Protozoa), we find the Sponges represented by the curious bodies, composed of netted fibres, to which the name of Protospongia has been given (fig. 32, a); and the comparatively gigantic, conical, or cylin- | F 82 HISTORICAL PALZZONTOLOGY. drical fossils termed Avcheocyathus by Mr Billings are certainly referable either to the Foraminifera or to the Sponges. ‘The almost total absence of lime- WF stones in the formation may Y be regarded as a sufficient ex- planation of tne fact that the Foraminifera are not more largely and unequivocally re- presented ; though the exist- ence of greensands in the Cambrian beds of Wisconsin and Tennessee may be taken as an indication that this class of animals was by no means wholly wanting. The same fact may explain the total ab- sence of corals, so far as at present known. The group of the Lchinoder- Fig. 29.—A portion of O/dhamia an- mata (Sea-lilies, Sea-urchins, tigua, Lower Cambrian, Wicklow, Ire- : : ° land, of the natural size. (After Salter.) | and their allies) is represented by a few forms, which are prin- cipally of interest as being the earliest-known examples of the class. It is also worthy of note that these precursors of a group which subsequently attains such geological importance, are referable to no less than three distinct orders—the Crinoids or Sea-lilies, represented by a species of Dendrocrinus; the Cystideans by Protocystites; and the Star-fishes by Padasterina and some other forms. Only the last of these groups, how- ever, appears to occur in the Lower Cambrian. The Ringed-worms (Annelida), if rightly credited with all the remains usually referred to them, appear to have swarmed in the Cambrian seas. Being soft-bodied, we do not find the actual worms themselves in the fossil condition, but we have, nevertheless, abundant traces of their existence. In some cases we find vertical burrows of greater or less depth, often expanded towards their apertures, in which the worm must have actually lived (fig. 30), as various species do at the pre- sent day. In these cases, the tube must have been rendered more or less permanent by receiving a coating of mucus, or perhaps a genuine membranous secretion, from the body of the animal, and it may be found quite empty, or occupied by a cast of sand or mud. Of this nature are the burrows which have been described under the names of Scolithus and Scoleco- derma, and probably the Aistioderma of the Lower Cambrian THE CAMBRIAN PERIOD. 83 of Ireland. In other cases, as in Arenicolites (fig. 32, 6), the worm seems to have inhabited a double burrow, shaped like an ra Te ZEB ————_— a ae c ae SEZ FE = = = = > =e ae S Fig. 30.—Annelide-burrows (Scolithus linearis), from the Potsdam Sandstone of Canada, of the natural size. (After Billings.) the letter U, and having two openings placed close together on the surface of the stratum. Thousands of these twin- burrows occur in some of the strata of the Longmynd, and it is supposed that the worm used one opening to the burrow as an aperture of entrance, and the other as one of exit. In other cases, again, we find simply the meandering trails caused by the worm dragging its body over the surface of the mud. Markings of this kind are commoner in the Silurian Rocks, and it is generally more or less doubtful whether they may not have been caused by other marine animals, such as shell- fish, whilst some of them have certainly nothing whatever to do with the worms. Lastly, the Cambrian beds often show twining cylindrical bodies, commonly more or less matted together, and not confined to the surfaces of the strata, but passing through them. These have often been regarded as the remains of sea-weeds, but it is more probable that they represent casts of the underground burrows of worms of simi- lar habits to the common lob-worm (A7enzcola) of the present day. The Articulate animals are numerously represented in the Cambrian deposits, but exclusively by the class of Crustaceans. Some of these are little double-shelled creatures, resembling our living water-fleas (Ostracoda). A few are larger forms, and belong to the same group as the existing brine-shrimps and fairy-shrimps (P%ylopfoda). One of the most characteristic of 84 HISTORICAL PALZONTOLOGY. these is the Wymenocaris vermicauda of the Lingula Flags (fig. 32, @). By far the larger number of the Cambrian Crustacea belong, however, to the remarkable and wholly extinct group of the Zyrzlobites. These extraordinary animals’ must have literally swarmed in the seas of the later portion of this and the whole of the succeeding period; and they survived in greatly diminished numbers till the earlier portion of the Carboniferous period. They died out, however, wholly before the close of the Paleozoic epoch, and we have no Crusta- ceans at the present day which can be considered as their direct representatives. They have, however, relationships of a more or less intimate character with the existing groups of the Phyllopods, the King-crabs (Zzmulus), and the Isopods (‘‘Slaters,” Wood-lice, &c.) Indeed, one member of the last- mentioned order, namely, the Sevo/zs of the coasts of Patagonia, has been regarded as the nearest living ally of the Trilobites. Be this as it may, the Trilobites possessed a skeleton which, though capable of undergoing almost endless variations, was wonderfully constant in its pattern of structure, and we may briefly describe here the chief features of this. The upper surface of the body of a Trilobite was defended by a strong shell or ‘‘ crust,” partly horny and partly calcare- ous in its composition. This shell (fig. 31) generally exhibits a very distinct “ trilobation” or division into three longitudinal lobes, one central and two lateral. It also exhibits a more important and more fundamental division into three transverse portions, which are so loosely connected with one another as very commonly to be found separate. The first and most anterior of these divisions is a shield or buckler which covers the head ; the second or middle portion is composed of mov- able rings covering the trunk (“thorax”); and the third is a shield which covers the tail or “abdomen.” ‘The head-shield (fig. 31, e) is generally more or less semicircular in shape ; and its central portion, covering the stomach of the animal, is usu- ally strongly elevated, and generally marked by lateral furrows. A little on each side of the head are placed the eyes, which are generally crescentic in shape, and resemble the eyes of insects and many existing Crustaceans in being ‘‘ compound,” or made up of numerous simple eyes aggregated together. So excellent is the state of preservation of many specimens of Trilobites, that the numerous individual lenses of the eyes have been uninjured, and as many as four hundred have been counted in each eye of some forms. ‘The eyes may be sup- ported upon prominences, but they are never carried on mov- able stalks (as they are in the existing lobsters and crabs) ; and THE CAMBRIAN PERIOD. 85 in some of the Cambrian Trilobites, such as the little Agwost7 (fig. 31, g), the animal was blind. The lateral portions of the Fig. 31.—Cambrian Trilobites: a, Pavadoxrides Bohenticus, reduced in size; 4, Ellif- socephalus Hoffi; c, Sao hirsuta; ad, Conocoryphe Sultzeri (all the above, together with fig. g, are from the Upper Cambrian or ‘‘ Primordial Zone” of Bohemia); ¢, Head-shield of Dikellocephalus Celticus, from the Lingula Flags of Wales; 4, Head-shield of Cozo- coryphe Matthewt, from the Upper Cambrian (Acadian Group) of New Brunswick; g, A gnostus rex, Bohemia ; 4, Tail-shield of Dikellocephalus Minnesotensis, from the Upper Cambrian (Potsdam Sandstone) of Minnesota. (After Barrande, Dawson, Salter, and Dale Owen.) head-shield are usually separated from the central portion by a peculiar line of division (the so-called ‘facial suture”) on each side; but this is alsa wanting in some of the Cambrian species. The backward angles of the head-shield, also, are often prolonged into spines, which sometimes reach a great length. Following the head-shield behind, we have a portion of the body which is composed of movable segments or ‘“‘body- rings,” and which is technically called the ‘‘ thorax.” Ordi- narily, this region is strongly trilobed, and each ring consists of a central convex portion, and of two flatter side-lobes. The number of body-rings in the thorax is very variable (from two to twenty-six), but is fixed for the adult forms of each group of the Trilobites. The young forms have much fewer rings than the full-grown ones ; and it is curious to find that the Cam- 86 HISTORICAL PALZONTOLOGY. brian Trilobites very commonly have either a great many rings (as in Paradoxides, fig. 31, a), or else very few (as in Agnostus, fig. 31, g). In some instances, the body-rings do not seem to have been so constructed as to allow of much movement, but in other cases this region of the body is so flexible that the animal possessed the power of rolling itself up completely, like a hedgehog ; and many individuals have been permanently preserved as fossils in this defensive condition. Finally, the body of the Trilobite was completed by a tail-shield (techni- cally termed the “‘pygidium”), which varies much in size and form, and is composed of a greater or less number of rings, similar to those which form the thorax, but immovably amalga- mated with one another (fig. 31, 7). The under surface of the body in the Trilobites appears to have been more or less entirely destitute of hard structures, with the exception of a well-developed upper lip, in the form of a plate attached to the inferior side of the head-shield in front. ‘There is no reason to doubt that the animal possessed legs; but these structures seem to have resembled those of many living Crustaceans in being quite soft and membranous. This, at any rate, seems to have been generally the case ; though structures which have been regarded as legs have been detected on the under surface of one of the larger species of Trilobites. There is also, at present, no direct evidence that the Trilobites possessed the two pairs of jointed feelers (‘‘an- tenne”) which are so characteristic of recent Crustaceans. The Trilobites vary much in size, and the Cambrian forma- tion presents examples of both the largest and the smallest members of the order. Some of the young forms may be little bigger than a millet-seed, and some adult examples of the smaller species (such as Agwostus) may be only a few lines in length ; whilst such giants of the order as Paradoxides and Asaphus may reach a length of from one to two feet. Judging from what we actually know as to the structure of the Tnilo- bites, and also from analogous recent forms, it would seem that these ancient Crustaceans were mud-haunting creatures, deni- zens of shallow seas, and affecting the soft silt of the bottom rather than the clear water above. Whenever muddy sedi- ments are found in the Cambrian and Silurian formations, there we are tolerably sure to find Trilobites, though they are by no means absolutely wanting in limestones. ‘They appear to have crawled about upon the sea-bottom, or burrowed in the yielding mud, with the soft under surface directed downwards; and it is probable that they really derived their nutriment from ‘the organic matter contained in the ooze amongst which they THE CAMBRIAN PERIOD. 87 lived. The vital organs seem to have occupied the central lobe of the skeleton, by which they were protected ; and a series of delicate leaf-like paddles, which probably served as respiratory organs, would appear to have been carried on the under surface of the thorax. ‘That they had their enemies may be regarded as certain; but we have no evidence that they were furnished with any offensive weapons, or, indeed, with any means of defence beyond their hard crust, and the power, possessed by so many of them, of rolling themselves into a ball. An addi- tional proof of the fact that they for the most part crawled along the sea-bottom is found in the occurrence of tracks and markings of various kinds, which can hardly be ascribed to any other creatures with any show of probability. That this is the true nature of some of the markings in question cannot be doubted at all; and in other cases no explanation so pro- bable has yet been suggested. If, however, the tracks which have been described from the Potsdam Sandstone of North America nnder the name of Protichnites are really due to the peregrinations of some Trilobite, they must have been pro- duced by one of the largest examples of the order. As already said, the Cambrian Rocks are very rich in the remains of Trilobites. In the lowest beds of the series (Long- mynd Rocks), representatives of some half-dozen genera have now been detected, including the dwarf Agwostus and the giant Paradoxidées. In the higher beds, the number both of genera and species is largely increased ; and from the great compara- tive abundance of individuals, the Trilobites have every right to be considered as the most characteristic fossils of the Cam- brian period,—the more so as the Cambrian species belong to peculiar types, which, for the most part, died out before the commencement of the Silurian epoch. All the remaining Cambrian fossils which demand any notice - here are members of one or other division of the great class of the Mollusca, or “ Shell-fish” properly so called. In the Lower Cambrian Rocks the Lamp-shells (Brachiopoda) are the principal or sole representatives of the class, and appear chiefly in three interesting and important types—namely, Zzzguleléa, Discina, and Obolelia. Of these the last (fig. 32, 2) is highly characteristic of these ancient deposits ; whilst Dzscima is one of those remarkable persistent types which, commencing at this early period, has continued to be represented by varying forms through all the intervening geological formations up to the present day. Lzngulella (fig. 32, c), again, is closely allied to the existing “‘ Goose-bill ” Lamp-shell (Zzngula anatina), and thus presents us with another example of an extremely long- 88 HISTORICAL PALZONTOLOGY. lived type. The Zzngulelle and their successors, the Lizgula, are singular in possessing a shell which is of a horny texture, and contains but a small proportion of calcareous matter. In the Upper Cambrian Rocks, the Zzmgulel/l@ become much more abundant, the broad satchel- shaped species known as JZ. Davisii (fig. 32, ¢) being:so abundant that one of the great divisions of the Cambrian is termed the “ Lingula Flags.” Here, also, we meet for the first time with examples of the genus Orthis (fig. 32, f, &, 2) a characteristic Paleozoic type of Fig. 32.—Cambrian Fossils : a, Protospongia fenestrata, Menevian Group; 6, Avrenz- colites didymus, Longmynd Group; c, Lingulella ferruginea, Longmynd and Meneyian, enlarged ; d, Hymenocaris vermicauda, Lingula Flags; e, Lingulella Davisii, Lingula Flags; 4, Orthis lenticularis, Lingula Flags; g, Theca Davidiz, Tremadoc Slates; %, Modiolopsis Solvensis, Vremadoc Slates; 7, Obolella sagittalis, interior of valve, Mene- vian; 7, Exterior of the same; 4, Orthis Hicksit, Menevian; 2, Cast of the same; mm, Olenus micrurus, Lingula Flags. (After Salter, Hicks, and Davidson.) the Brachiopods, which is destined to undergo a vast extension in later ages. Of the higher groups of the A7Zo//usca the record is as yet but scanty. In the Lower Cambrian, we have but the thin, fragile, dagger-shaped shells of the free - swimming oceanic Molluscs or “ Winged-snails” (P¢eropoda), of which the most characteristic is the genus Zheca (fig. 32, g). In the Upper Cambrian, in addition to these, we have a few Univalves (Gasteropoda), and, thanks to the researches of Dr Hicks, quite a small assemblage of Bivalves (Lamedlibranchiata), though these are mostly of no great dimensions (fig. 32, 7). Of the chambered Cephalopoda (Cuttle-fishes and their allies), THE CAMBRIAN PERIOD. 89 we have but few traces, and these wholly confined to the higher beds of the formation. We meet, however, with examples of the wonderful genus Orthoceras, with its straight, partitioned shell, which we shall find in an immense variety of forms in the Silurian rocks. Lastly, it 1s worthy of note that the lowest of all the groups of the JAZollusca — namely, that of the Sea- mats, Sea-mosses, and Lace-corals (Po/y- zoa)—1is only doubtfully known to have any representatives in the Cambrian, though undergoing a large and varied development in the Silurian deposits. An exception, however, may with much Ht probability be made to this statement in Hint so Fsementiak favour of the singular genus Dayctyonema Dictyonema soctale, con- ; : : ote siderably enlarged, show- (fig. 33), which is highly characteristic of ing the horny branches, the jhighest Cambrian, beds (Tremadoc .. ti ten, comers Slates). This curious fossil occurs in the of cells on each side. form of fan-like or funnel-shaped expan- (0™8'*") sions, composed of slightly-diverging horny branches, which are united in a net-like manner by numerous delicate cross- bars, and exhibit a row of little cups or cells, in which the ani- mals were contained, on each side. Dzctyonema has generally been referred to the Graf/olites ; but it has a much greater affinity with the plant-like Sea-firs (Sertudarians) or the Sea- mosses (/Polyzoa), and the balance of evidence is perhaps in favour of placing it with the latter. LITERATURE. The following are the more important and accessible works and memoirs which may be consulted in studying the stratigraphical and palzontolo- gical relations of the Cambrian Rocks :— (1) ‘Siluria.” Sir Roderick Murchison. 5th ed., pp. 21-46. (2) ‘Synopsis of the Classification of the British Palzeozoic Rocks.’ Sedgwick. Introduction to the 3d Fasciculus of the ‘ Descrip- tions of British Palzeozoic Fossils in the Woodwardian Museum,’ by F. M‘Coy, pp. i-xcviii, 1855: (3) ‘Catalogue of the Cambrian and Silurian Fossils in the Geological Museum of the University of Cainbridge.’ Salter. With a Pref- ace by Prof. Sedgwick. 1873. (4) ‘Thesaurus Siluricus.’ Bigsby. 1868. (5) ‘‘ History of the Names Cambrian and Silurian.” Sterry Hunt.— ‘Geological Magazine.’ 1873. (6) ‘Systeme Silurien du Centre de la Bohéme.’ Barrande. Vol. I. (7) ‘ Report of Progress of the Geological Survey of Canada, from its Commencement to 1863,’ pp. 87-109. x gO HISTORICAL PALAZON TOLOGY. (8) ‘Acadian Geology.” Dawson. Pp. 641-657. (9) ‘* Guide to the Geology of New York,” Lincklaen; and ‘‘ Contribu- tions to the Palzontology of New York,” James Hall.—‘ Four- teenth Report on the State Cabinet.’ 1861. (10) ‘ Palzeozoic Fossils of Canada.’ Billings. 1865. (11) ‘ Manual of Geology,’ Dana. Pp. 166-182. 2d ed. 1875. (12) ‘‘Geology of North Wales,” Ramsay; with Appendix on the Fossils, Salter.—‘ Memoirs of the Geological Survey of Great Britain,’ vol. iii. 1866, (13) ‘‘Onthe Ancient Rocks of the St David’s Promontory, South Wales, and their Fossil Contents.” Harkness and Hicks.—‘ Quart. Journ. Geol. Soc.,’ xxvii. 384-402. 1871. (14) *fOn the Tremadoc Rocks in the Neighbourhood of St David’s, South Wales, and their Fossil Contents.” Hicks.—‘ Quart. Journ: Geol: Soc:,' xxix. 30-52. 21873. In the above list, allusion has necessarily been omitted to numerous works and memoirs on the Cambrian deposits of Sweden and Norway, Central Europe, Russia, Spain, and various parts of North America, as well as to a number of important papers on the British Cambrian strata by various well-known observers. Amongst these latter may be mentioned memoirs by Prof. Phillips, and Messrs Salter, Hicks, Belt, Plant, Hom- fray, Ash, Holl, &c. CHAE ER ik THE LOWER SILORIAW PERTOU: The great system of deposits to which Sir Roderick Murchi- son applied the name of ‘Silurian Rocks” reposes directly upon the highest Cambrian beds, apparently without any marked unconformity, though with a considerable change in the nature of the fossils. The name ‘‘ Silurian” was originally proposed by the eminent geologist just alluded to for a great series of strata lying below the Old Red Sandstone, and occu- pying districts in Wales and its borders which were at one time inhabited by the ‘‘Silures,” a tribe of ancient Britons. Deposits of a corresponding age are now known to be largely developed in other parts of England, in Scotland, and in Ire- land, in North America, in Australia, in India, in Bohemia, Saxony, Bavaria, Russia, Sweden and Norway, Spain, and in various other regions of less note. In some regions, as in the neighbourhood of St Petersburg, the Silurian strata are found not only to have preserved their original horizontality, but also to have retained almost unaltered their primitive soft and inco- herent nature. In other regions, as in Scandinavia and many THE LOWER SILURIAN PERIOD. QI parts of North America, similar strata, now consolidated into shales, sandstones, and limestones, may be found resting with a very slight inclination on still older sediments. In a great many regions, however, the Silurian deposits are found to have undergone more or less folding, crumpling, and dislocation, accompanied by induration and ‘‘cleavage” of the finer and softer sediments ; whilst in some regions, as in the Highlands of Scotland, actual “metamorphism” has taken place. In - consequence of the above, Silurian districts usually present the bold, rugged, and picturesque outlines which are char- acteristic of the older ‘‘ Primitive” rocks of the earth’s crust in general. In many instances, we find Silurian strata rising into mountain-chains of great grandeur and sublimity, exhibiting the utmost diversity of which rock-scenery is capable, and de- lighting the artist with endless changes of valley, lake, and cliff. Such districts are little suitable for agriculture, though this is often compensated for by the valuable mineral products con- tained in the rocks. On the other hand, when the rocks are tolerably soft and uniform in their nature, or when few disturb- ances of the crust of the earth have taken place, we may find Silurian areas to be covered with an abundant pasturage or to be heavily timbered. Under the head of “Silurian Rocks,” Sir Roderick Murchi- son included all the strata between the summit of the ‘‘ Long- mynd” beds and the Old Red Sandstone, and he divided these into the two great groups of the Zower Silurian and Upper Silu- rian. It is, however, now generally admitted that a considerable portion of the basement beds of Murchison’s Silurian series must be transferred—if only upon palzeontological grounds—to the Upper Cambrian, as has here been done; and much contro- versy has been carried on as to the proper nomenclature of the Upper Silurian and of the remaining portion of Murchison’s Lower Silurian. Thus, some would confine the name “ Silu- rian” exclusively to the Upper Silurian, and would apply the name of ‘ Cambro-Silurian” to the Lower Silurian, or would include all beds of the latter age in the ‘‘ Cambrian” series of Sedgwick. It is not necessary to enter into the merits of these conflicting views. For our present purpose, it is sufficient to recognise that there exist two great groups of rocks between the highest Cambrian beds, as here defined, and the base of the Devonian or Old Red Sandstone. These two great groups are so closely allied to one another, both physically and pale- ontologically, that many authorities have established a third or intermediate group (the “ Middle Silurian”), by which a pas- Q2 HISTORICAL PALAEONTOLOGY. sage is made from one into the other. This method of pro- cedure involves RY oS which appear to outweigh its advantages ; and the two groups in question are not only gen- erally capable of very distinct stratigraphical separation, but at the same time exhibit, together with the alliances above spoken of, so many and such important paleontological differences, that it is best to consider them separately. We shall there- fore follow this course in the present instance ; and pending the final solution of the controversy as to Cambrian and Silu- rian nomenclature, we shall distinguish these two groups of strata as the ‘* Lower Silurian” and the “ Upper Silurian.” The Lower Silurian Rocks are known already to be devel- oped in various regions ; and though their gewera/ succession in these areas is approximately the same, each area exhibits peculiarities of its own, whilst the subdivisions of each are known by special names. All, therefore, that can be attempted here, is to select two typical areas—such as Wales and North America—and to briefly consider the grouping and divisions of the Lower Silurian in each. In Wales, the line between the Cambrian and Lower Silurian is somewhat ill-defined, and is certainly not marked by any strong unconformity. There are, however, grounds for accept- ing the line proposed, for paleontological reasons, by Dr Hicks, in accordance with which the Tremadoc Slates (‘‘ Lower Tremadoc” of Salter) become the highest of the Cambrian deposits of Britain. If we take this view, the Lower Silurian rocks of Wales and adjoining districts are found to have the piste general succession from below upwards (fig. 34):— The Arenig Group.—This group derives its name from the ‘Arenig mountains, where it is extensively developed. It consists of about 4000 feet of slates, shales, and flags, and is divisible into a lower, middle, and upper division, of which the former is often regarded as Cambrian under the name of “ Upper Tremadoc Slates.” 2. The Llandeilo Group.—The thickness of this group varies from about 4000 to as much as 10,000 feet; but in this latter case a great amount of the thickness is made up of volcanic ashes and interbedded traps. The sedimentary beds of this group are principally slates and flags, the latter occasionally with calcareous bands; and the whole series can be divided into a lower, middle, and upper Llandeilo division, of which the last is the most important. The name of “ Llandeilo” 1 derived from the town of the same name in Wales, where strata of this age were described by Murchison. THES LOWER» SILURIAN: PERIOD. 93 3. The Caradoc or Bala Group.—The alternative names of this group are also of local origin, and are derived, the one from Caer Caradoc in Shropshire, the other from Bala in Wales, strata of this age occurring in both localities. The series is divided into a lower and upper group, the latter chiefly com- posed of shales and flags, and the former of sandstones and shales, together with the important and interesting calcareous band known as the “ Bala Limestone.” ‘The thickness of the entire series varies from 4000 to as much as 12,000 feet, ac- cording: as it contains more or less of interstratified igneous rocks. 4. The Llandovery Group (Lower Llandovery of Murchison). —This series, as developed near the town of Llandovery, in Caermarthenshire, consists of less than tooo feet of conglom- erates, sandstones, and shales. It is probable, however, that the little calcareous band known as the “ Hirnant Limestone,” together with certain pale-coloured slates which lie above the Bala Limestone, though usually referred to the Caradoc series, should in reality be regarded as belonging to the Llandovery group. The general succession of the Lower Silurian strata of Wales and its borders, attaining a maximum thickness (along with contemporaneous igneous matter) of nearly 30,000 feet, is diagramatically represented in the annexed sketch-section (fig. 34) :— [GENERALISED SECTION Q4. HISTORICAL PALAEONTOLOGY. GENERALISED SECTION OF THE LOWER SILURIAN ROCKS OF WALES. Fig. 34. May Hill Sandstone (base of Upper Silurian). VERY GROUP. Llandovery Group. LLANDO- Upper Bala. Lower Bala. CARADOC OR BALA GROUP. eB Upper Llandeilo. S oO = Middle Llandeilo. fz) a Z 5 Lower Llandeilo. ao | . Upper Arenig. = ===! 2 aS=SS=SSSSSSSSS__===S== Cpl a Sema MR ee 0 (PEATE J Ved ef pe Ry 7 eT 4 Lower Arenig (Upper ——— ne Tremadoc Group). SSSSS———__—__==========——=aa—S]]S== SaSSSSS__=_=_=======Sa== Tremadoc Slates (Lower —aSSSSSSSa==—]]—S" Tremadoc Group). In North America, both in the United States and in Can- ada, the Silurian rocks are very largely developed, and may be THE LOWER SILURIAN PERIOD. 95 regarded as constituting an exceedingly full and typical series of the deposits of this period. The chief groups of the Silurian rocks of North America are as follows, beginning, as before, with the lowest strata, and proceeding upwards (fig. 35) :— 1. Quebec Group. — This group is typically developed in the vicinity of Quebec, where it consists of about 5000 feet of strata, chiefly variously - coloured shales, together with some sandstones and a few calcareous bands. It contains a number of peculiar Graptolites, by which it can be identified without question with the Arenig group of Wales and the correspond- ing Skiddaw Slates of the North of England. It is also to be noted that numerous Trilobites of a distinct Cambrian /aczes have been obtained in the limestones of the Quebec group, near Quebec. These fossils, however, have been exclusively obtained from the limestones of the group; and as these lime- stones are principally calcareous breccias or conglomerates, there is room for believing that these primordial fossils are really derived, in part at any rate, from fragments of an upper Cambrian limestone. In the State of New York, the Grapto- litic shales of Quebec are wanting ; and the base of the Silurian is constituted by the so-called ‘ Calciferous Sand-rock” and ‘“‘Chazy Limestone.”* The first of these is essentially and typically calcareous, and the second is a genuine limestone. 2. The Zrenton Group.—This is an essentially calcareous group, the various. limestones of which it is composed being known as the “ Bird’s-eye,” ‘“‘ Black River,” and ‘“‘ Trenton” Limestones, of which the last is the thickest and most import- ant. ‘The thickness of this group is variable, and the bands of limestone in it are often separated by beds of shale. 3. The Cincinnati Group (Hudson River Formation t).— This group consists essentially of a lower series of shales, often black in colour and highly charged with bituminous matter (the ‘“ Utica Slates”), and of an upper series of shales, sand- * The precise relations of the Quebec shales with Graptolites (Levis Formation) to the Calciferous and Chazy beds are still obscure, though there seems little doubt but that the Quebec Shales are superior to the Calciferous Sand-rock. + There is some difficulty about the precise nomenclature of this group. It was originally called the ‘‘ Hudson River Formation; ” but this name is inappropriate, as rocks of this age hardly touch anywhere the actual Hudson River itself, the rocks so called formerly being now known to be of more ancient date. There is also some want of propriety in the name of ‘Cincinnati Group,” since the rocks which are known under this name in the vicinity of Cincinnati itself are the representatives of the -Trenton Limestone, Utica Slates, and the old Hudson River group, inseparably united in what used to be called the ‘* Blue Limestone Series.” 96 HISTORICAL PALEONTOLOGY. stones, and limestones (the “‘ Cincinnati” rocks proper). The exact parallelism of the Trenton and Cincinnati groups with the subdivisions of the Welsh Silurian series can hardly be stated positively. Probably no precise equivalency exists ; but there can be no doubt but that the Trenton and Cincin- nati groups correspond, as a whole, with the Llandeilo and Caradoc groups of Britain. The subjoined diagrammatic section (fig. 35) gives a general idea of the succession of the Lower Silurian rocks of North America :— GENERALISED SECTION OF THE LOWER SILURIAN ROCKS OF NORTH AMERICA. Fig. 35. Medina Sandstone (base of Upper Silurian). 5 O Z - Cincinnati Group proper. > = Z, is oO 2 =------ Utica Slates. a 5 4 A Sete = ~Trenton Limestone. >) S s LL a) 0) 0 Se eee ee ee eee ee -Black River Limestone. 4 arencrge VO) Pe ie Wa On ee Bird’s-eye Limestone. a (Tt].----.-Chazy Limestone. Y => 5 5 a =... (Quebec Shales (Levis Beds). es = & = oem CE et a ee aay eee ..Calciferous Sand-rock. ee BS Potsdam Sandstone. THE LOWER SILURIAN. PERIOD. C7 Of the Zfe of the Lower Silurian period we have record in a vast number of fossils, showing that the seas of this period were abundantly furnished with living denizens. We have, however, in the meanwhile, no knowledge of the land-surfaces of the period. We have therefore no means of speculating as to the nature of the terrestrial animals of this ancient age, nor is anything known with certainty of any land-plants which may have existed. The only relics of vegetation upon which a positive opinion can be expressed belong to the obscure group of the “ Fucoids,” and are supposed to be the remains of sea-weeds. Some of the fossils usually placed under this head are probably not of a vegetable nature at all, but others / A \ f f YJ .»** i / Ui, / Y j GY, Y Uf SF i a IM Poyalvry, / ] VW yh . Fig. 36.—Licrophycus Ottawaensis, a ‘‘ Fucoid.” from the Trenton Limestone (Lower Silurian) of Canada. (After Billings.) (fig. 36) appear to be unquestionable plants. The true affin- ities of these, however, are extremely dubious. All that can be said ig, that remains which appear to be certainly vegetable, ‘ G 98 HISTORICAL. PALAZAON TOLOGY. and which are most probably due to marine plants, have been recognised nearly at the base of the Lower Silurian (Arenig), and that they are found throughout the series whenever suitable conditions recur. The Protozoans appear to have flourished extensively in the Lower Silurian seas, though to a large extent under forms which are still little understood. We have here for the first time the appearance of /oraminifera of the ordinary type—one of the most interesting observations in this connection being that made by Ehrenberg, who showed that the Lower Silunan sandstones of the neighbourhood of St Petersburg contained casts in glauconite of Foraminiferous shells, some of which are referable to the existing genera Rofalia and Zextularia. ‘True Sponges, belonging to that section of the group in which the skeleton is calcareous, are also not unknown, one of the most characteristic genera being As- tylospongia (fig. 37). In this genus are included more or less globular, often lobed sponges, which are believed not to have been attached toforeign bodies. In the form here figured there is a funnel-shaped cavity at the summit; and the entire mass of the sponge is perforated, as in living examples, by a system of canals which convey the sea-water to all parts of the Fig. 37.—Astylospongia premorsa, cut organism. The canals by vertically so as to exhibit the canal-system which the sea-water gains en- intheinterior. Lower Silurian, Tennessee. : = : (After Retdinand Rosner) trance open on the exterior of the sphere, and those by which it again escapes from the sponge open into the cup-shaped depression at the summit. The most abundant, and at the same time the least under- stood, of Lower Silurian Protozoans belong, however, to the genera Stromatopora and Receptaculites, the structure of which can merely be alluded to here. The specimens of Stromato- pora (fig. 38) occur as hemispherical, pear-shaped, globular, or irregular masses, often of very considerable size, and some- times demonstrably attached to foreign bodies. In their struc- ture these masses consist of numerous thin calcareous lamine, usually arranged concentrically, and separated by narrow interspaces. ” These interspaces are generally crossed by numerous vertical calcareous pillars, giving the vertical section iat LOWER -SIEURTAN PERIOD: 99 of the fossil a lattice-like appearance. There are also usually minute pores in the concentric laminze, by which the successive Fig. 38.—A small and perfect specimen of Stromatopora rugosa, of the natural size, from the Trenton Limestone of Canada. (After Billings.) interspaces are placed in communication ; and sometimes the surface presents large rounded openings, which appear to corre- spond with the water-canals of the Sponges. Upon the whole, though presenting some curious affinities to the calcareous Sponges, Stromatopora 1s perhaps more properly regarded as a gigantic Foraminifer. If this view be correct, it is of special interest as being probably the nearest ally of Lozoon, the general appearance of the two being strikingly similar, though their minute structure is not at all the same. Lastly, in the fossils known as Receptaculites and /schadites we are also pre- sented with certain singular Lower Silurian Protozoans, which may with great probability be regarded as gigantic /oramu- nifera. Their structure is very complex; but fragments are easily recognised by the fact that the exterior is covered with numerous rhomboidal calcareous plates, closely fitting together, and arranged in peculiar intersecting curves, presenting very much the appearance of the engine-turned case of a watch. Passing next to the sub-kingdom of Cae/enterate animals (Zoophytes, Corals, &c.), we find that this great group, almost or wholly absent in the Cambrian, is represented in Lower 100 HISTORICAL PALZONTOLOGY. Silurian deposits by a great number of forms belonging on the one hand to the true Corals, and on the other hand to the singular family of the Graptolites. If we except certain plant- like fossils which probably belong rather to the Sertularians or the Polyzoans (2 g., Ductyonema, Dendrograptus, &c.), the family of the Grapéolites may be regarded as exclusively Silurian in its distribution. Not only is this the case, but it attained its maximum development almost upon its first ap- pearance, in the Arenig Rocks; and whilst represented by a great variety of types in the Lower Silurian, it only exists in the Upper Silurian in a much diminished form. The Grap- tolites (Gr. grapho, I write; ¢thos, stone) were so named by Linneeus, from the resemblance of some of them to written or pencilled marks upon the stone, though the great naturalist him- self did not believe them to be true fossils at all. They occur as linear or leaf-like bodies, sometimes simple, sometimes com- pound and branched; and no doubt whatever can be enter- tained as to their being the skeletons of composite organisms, or colonies of semi-independent animals united together by a common fleshy trunk, similar to what is observed in the colonies of the existing Sea-firs (Sertularians). This fleshy trunk or common stem of the colony was protected by a deli- cate horny sheath, and it gave origin to the little flower-like “polypites,” which constituted the active element of the whole assemblage. These semi-independent beings were, in turn, protected each by a little horny cup or cell, directly connected with the common sheath below, and terminating above in an opening through which the polypite could protrude its tentacled head or could again withdraw itself for safety. ‘The entire skeleton, again, was usually, if not universally, supported by a delicate horny rod or ‘‘axis,” which appears to have been hollow, and which often protrudes to a greater or less extent beyond one or both of the extremities of the actual colony. The above gives the elementary constitution of any Grafio- lite, but there are considerable differences as to the manner in which these elements are arranged and combined. In some forms the common stem of the colony gives ongin to but a single row of cells on one side. If the common stem is a simple, straight, or slightly-curved linear body, then we have the simplest form of Graptolite known (the genus AZonograptus) ; and it is worthy of note that these simple types do not come into existence till comparatively late (Llandeilo), and last nearly to the very close of the Upper Silurian. In other cases, whilst there is still but a single row of cells, the colony may consist of two of these simple stems springing from a THE LOWER. SILURIAN PERIOD. IOL common point, as in the so-called “twin Graptolites ” (Dzdy- mograptus, fig. 40). This type is entirely confined to the earlier portion of the Lower Silu- rian period (Arenig and Llandeilo). In other cases, again, there may be four of such stems springing from acentral point (Zé?- ragraplus). Lastly, there are numerous complex forms (such as Dichograp- tus, Loganograptus, &c.) which there are eight or more of these simple bran- ches, all arising from a common centre (fig. 39), which is sometimes fur- nished with a_ singular horny disc. These com- plicated branching forms, as well as the Zetragrapiz, are characteristic of the horizon of the Arenig group. Similar forms, of- ten specifically identical, Fig. 39.—Dichograptus octobrachiatus, a branched, “unicellular” Graptolite from the Skiddaw and Quebec Groups (Arenig). (After Hall.) are found at this horizon in Wales, in the great series of the Skiddaw Slates of the north of England, in the Quebec group in Canada, in equivalent beds in Sweden, and in certain gold- bearing slates of the same age in Victoria in Australia. In another great group of Graptolites (including the genera Diplograptus, Dicranograptus, Climacograptus, &c.) the common stem of the colony gives origin, over part or the whole of its length, to ‘wo rows of cells, one on each side (fig. 41). These double-celled ” Graptolites are highly characteristic of the Lower Silurian deposits; and, with an exception more appa- 102 HISTORICAL PALAZONTOLOGY. rent than real in Bohemia, they are exclusively confined to strata of Lower Silurian age, and are not known to occur in Fig. 40.—Central portion of the colony of Didymograptus divaricatus, Upper Llandeilo, Dumfriesshire. (Original.) the Upper Silurian. Lastly, there is a group of Graptolites (Phyllograptus, fig. 42) in which the colony is leaf-like in form, TA =F q wry rips 6 Fig. 41.—Examples of Diplograptus pristis, showing variations in the appen- dages at the base. Fig. 42.—Group of individuals of Phyddo- Dumfriesshire. graptus typus, from the Quebec group of Upper Llandeilo, Canada. (After Hall.) One of the four rows (Original.) of cells is hidden on the under surface. and is composed of fowr rows of cells springing in a cross-like THE LOWER SILURIAN PERIOD. 103 manner from the common stem. These forms are highly char- acteristic of the Arenig group. The Graptolites are usually found in dark-coloured, often black shales, which sometimes contain so much carbon as to become “anthracitic.” They may be simply carbonaceous; but they are more commonly converted into iron-pyrites, when they glitter with the brilliant lustre of silver as they lie scattered on the surface of the rock, fully deserving in their metallic tracery the name of “written stones.” They constitute one of the most important groups of Silurian fossils, and are of the greatest value in determining the precise stratigraphical posi- tion of the beds in which they occur. They present, however, special difficulties in their study ; and it is still a moot point as to their precise position in the zoological scale. The balance of evidence is in favour of regarding them as an ancient and peculiar group of the Sea-firs (Hydroid Zoophytes), but some regard them as belonging rather to the Sea-mosses (Polyzoa). Under any circumstances, they cannot be directly compared either with the ordinary Sea-firs or the ordinary Sea-mosses ; for these two groups consist of fixed organisms, whereas the Graptolites were certainly free-floating creatures, living at large in the open sea. The only Hydroid Zoophytes or Poly- zoans which have a similar free mode of existence, have either no skeleton at all, or have hard structures quite unlike the horny sheaths of the Graptolites. The second great group of Coelenterate animals (Actinozoa) is represented in the Lower Silurian rocks by numerous Corals. These, for obvious reasons, are much more abundant in regions where the Lower Silurian series is largely calcareous (as in North America) than in districts ike Wales, where limestones are very feebly developed. The Lower Silunan Corals, though the first of their class, and presenting certain pecuharities, may be regarded as essentially similar in nature to existing Corals. These, as is well known, are the calcareous skeletons of animals —the so-called ‘ Coral-Zoophytes ”— closely allied to the common Sea-anemones in strugture and habit. A szmple coral (fig. 43) consists of a calcareous cup embedded in the soft tissues of the flower-like polype, and hay- ing at its summit a more or less deep depression (the ‘ calice’’) in which the digestive organs are contained. The space within the coral is divided into compartments by numerous vertical calcareous plates (the “‘ septa”), which spring from the inside of the wall of the cup, and of which some generally reach the centre. Compound corals, again (fig. 44), consist of a greater or less number of structures similar in structure to the above, 104 HISTORICAL PALZZONTOLOGY. but united together in different ways into a common mass. Simple corals, therefore, are the skeletons of szzgZe and inde- big. 43.— Zaphrentis Stokesi, a simple Fig. 44.—Upper surface of a mass of ‘“cup-coral,” Upper Silurian, Canada. (After Stronzbodes pentagonus, Upper Silurian, Billings.) Canada. (After Billings.) pendent polypes ; whilst compound corals are the skeletons of assemblages or colonies of similar polypes, living united with one another as an organic community. In the general details of their structure, the Lower Silurian Corals do not differ from the ordinary Corals of the present day. The latter, however, have the vertical calcareous plates of the coral (“‘septa”) arranged in multiples of six or five; whereas the former have these structures arranged in multiples of four, and often showing a cross-like disposition. For this reason, the common Lower Silurian Corals are separated to form a distinct group under the name of Augose Corals or Rugosa. They are further distinguished by the fact that the cavity of the coral (“ visceral chamber ”) is usually subdivided by more or less numerous Aorzzontal calcareous plates or partitions, which divide the coral into so many tiers or storeys, and which are known as the “tabula” (fig. 45). In addition to the Rugose Corals, the Lower Silurian rocks contain a number of curious compound corals, the tubes of which have either no septa at all or merely rudimentary ones, but which have the transverse partitions or ‘ tabule ” very highly developed. These are known as the Zadulate Corals ; and recent researches on some of their existing allies (such as /Zeliofora) have shown that they are really allied to THE LOWER SILURIAN, PERIOD. 105 the modern Sea-pens, Organ-pipe Corals, and Red Coral, rather than to the typical stony Corals. Amongst the charac- Fig. 45.—Columnaria alveolata, a Rugose compound coral, with imperfect septa, but having the corallites partitioned off into storeys by ‘‘tabulz.” Lower Silurian, Canada. (After Billings.) teristic Rugose Corals of the Lower Silurian may be mentioned species belonging to the genera Col/umnaria, Favistella, Strep- telasma, and Zaphrentis; whilst amongst the ‘“ Tabulate” Corals, the principal forms belong to the genera Chetretes, Halysites (the Chain-coral), Cozstellaria,and Heliolites. ‘These groups of the Corals, however, attain a greater development at a later period, and they will be noticed more particularly hereafter. Passing on to higher animals, we find that the class of the Echinodermata is represented by examples of the Star-fishes ( Asteroidea), the Sea-lilies (Crinoidea), and the peculiar extinct group of the Cystideans (Cys¢oddea), with one or two of the Brittle-stars (OpAiurotdea)—the Sea-urchins (Echinoidea) being still wanting. The Crinoids, though in some places extremely numerous, have not the varied development that they possess in the Upper Silurian, in connection with which their structure will be more fully spoken of. In the meanwhile, it is sufficient to note that many of the calcareous deposits of the Lower Silurian are strictly entitled to the name of ‘ Crinoidal lime- stones,” being composed in great part of the detached joints, and plates, and broken stems, of these beautiful but fragile organisms (see fig. 12). Allied to the Crinoids are the singular creatures which are known as Cystideans (fig. 46). These are generally composed of a globular or ovate body (the “ calyx”), supported upon a short stalk (the ‘ column”), by which the organism was usually attached to some foreign body. ‘The body was enclosed by closely-fitting calcareous plates, accu- 106 HISTORICAL PALAONTOLOGY. rately jointed together ; and the stem was made up of numerous distinct pieces or joints, flexibly united to each other by mem- Fig. 46.—Group of Cystideans. A, Caryocrinus ornatus,* Upper Silurian, America; B, Pleurocystites sguantosus, showing two short ‘‘arms,” Lower Silurian, Canada; C, Pseudocrinus bifasciatus, Upper Silurian, England ; D, Lepadocrinus Gebhardi, Upper Silurian, America. (After Hall, Billings, and Salter.) brane. The chief distinction which strikes one in comparing the Cystideans with the Crinoids is, that the latter are always furnished, as will be subsequently seen, with a beautiful crown of branched and feathery appendages, springing from the sum- mit of the calyx, and which are composed of innumerable calcareous plates or joints, and are known as the ‘‘arms.” In the Cystideans, on the other hand, there are either no “arms” at all, or merely short, unbranched, rudimentary arms. ‘The Cystideans are principally, and indeed nearly exclusively, Silurian fossils; and though occurring in the Upper Silurian in no small numbers, they are pre-eminently characteristic of the Llandeilo-Caradoc period of Lower Silurian time. ‘They commenced their existence, so far as known, in the Upper Cambrian; and though examples are not absolutely unknown * The genus Caryocrinus is sometimes regarded as properly belonging to the Cr7znoids, but there seem to be good reasons for rather considering it as an abnormal form of Cystidean. THE LOWER SILURIAN, PERIOD. 107 in later periods, they are pre-eminently characteristic of the earlier portion of the Palzeozoic epoch. The Ringed Worms (Azmelzdes) are abundantly represented in the Lower Silurian, but principally by tracks and burrows similar in essential respects to those which occur so commonly in the Cambrian formation, and calling for no special com- ment. Much more important are the Articulate animals, rep- resented, as heretofore, wholly by the remains of the aquatic pai 4 UB A\\ \\g Ye a | i —S } S SY / Fig. 47.—Lower Silurian Crustaceans. a, Asaphus tyrannus, Upper Llandeilo; 4, Ogygia Buchii, Upper Llandeilo; c, Txtnucleus concentricus, Caradoc; ad, Caryocarts Wrightii, Arenig (Skiddaw Slates) ; e, Beyrichia conzplicata, natural size and enlarged, Upper Llandeilo and Caradoc; f, Primitia strangulata, Caradoc: g, Head-shield of Calymene Blumenbachii, var. brevicapitata, Caradoc; h, Head-shield of Triarthrus Becki (Utica Slates), United States; z, Shield of Leferditia Canadensis, var. Yoseph- zana, of the natural size, Trenton Limestone, Canada; 7, The same, viewed from the front. (After Salter, M‘Coy, Rupert Jones, and Dana.) group of the Crustaceans. Amongst these are numerous little bivalved forms—such as species of Primitia (fig. 47, f), Bey- 108 HISTORICAL PALAZONTOLOGY. richia (fig. 47, e), and Leperditia (fig. 47, ¢ and 7). Most of these are very small, varying from the size of a pin’s head up to that of a hemp seed; but they are sometimes as large as a small bean (fig. 47, z), and they are commonly found in myriads together in the rock. As before said, they belong to the same great group as the living Water-fleas (Ostracoda). Besides these, we find the pod-shaped head-shields of the shrimp-like Phyllopods—such as Caryocaris (fig. 47, @) and Ceratiocaris. More important, however, than any of these are the Z7ilobites, which may be considered as attaining their maxi- mum development in the Lower Silurian. The huge Paradoxides of the Cambrian have now disappeared, and with them almost all the principal and characteristic ‘‘ primordial” genera, save Olenus and Agnostus. In their place we have a great number of new forms—some of them, like the great Asaphus tyrannus of the Upper Llandeilo (fig. 47, @), attaining a length of a foot or more, and thus hardly yielding in the matter of size to their ancient rivals. Almost every subdivision of the Lower Silurian series has its own special and characteristic species of Tnlo- bites ; and the study of these is therefore of great importance to the geologist. A few widely-dispersed and characteristic species have been here figured (fig. 47); and the following may be considered as the principal Lower Silurian genera— Asaphus, Ogygia, Chetrurus, Ampyx, Calymene, Trinucleus, Lichas, LMenus, Aglina, Harpes, Remopleurides, Phacops, Acidaspis, and Homalonotus, a few of them passing upwards under new forms into the Upper Silurian. Coming next to the AZo//usca, we find the group of the Sea- mosses and Sea-mats (Po/yzoa) represented now by quite a number of forms. Amongst these are examples of the true _ Lace-corals (Retepora and Fenestella), with their netted fan-like or funnel-shaped fronds; and along with these are numerous delicate encrusting forms, which grew parasitically attached to shells and corals (Hipfothoa, Alecto, &c.); but perhaps the most characteristic forms belong to the genus P¢/odictya (figs. 48 and 49). In this group the frond is flattened, with thin striated edges, sometimes sword-like or scimitar-shaped, but often more or less branched ; and it consists of two layers of cells, separated by a delicate membrane, and opening upon opposite sides. Each of these little chambers or “ cells” was originally tenanted by a minute animal, and the whole thus constituted a compound organism or colony. The Lamp-shells or 4rachiopods are so numerous, and pre- sent such varied types, both in this and the succeeding period of the Upper Silurian, that the name of “ Age of Brachiopods” THE LOWER SILURIAN PERIOD. ICQ has with justice been applied to the Silurian period as a whole. It would be impossible here to enter into details as to the © ESI L010 6; a it, i ; >) Fig. 48.—Ptilodictya falciformis. a, Fig. 49.—A, Ptilodictya acuta ; B, Ptit- Small specimen of the natural size; 6, odictya Schafferi. a, Fragment, of the Cross-section, showing the shape of the natural size; 4, Portion, enlarged to show frond ; c, Portion of the surface, enlarged. the cells. Cincinnati Group of Ohio and Trenton Limestone and Cincinnati Group, Canada. (Original.) America. (Original.) many different forms of Brachiopods which present themselves in the Lower Silurian deposits; but we may select the three genera Orthis, Strophomena, and Leftena for illustration, as being specially characteristic of this period, though not exclu- Fig. 50.—Lower Silurian Brachiopods. a@ and a’, Orthis béforata, Llandeilo-Caradoc, Britain and America; 6, Orthis flabellulum, Caradoc, Britain; c, Orthis subguadrata, Cincinnati Group, America ; c’, Interior of the dorsal valve of the same; d, S¢ropho- dia gga Llandeilo-Caradoc, Britain and America. (After Meek, Hall, and alter. sively confined to it. The numerous shells which belong to the extensive and cosmopolitan genus O7rthis (fig. 50, a, 3, 6, IIo HISTORICAL PALAEONTOLOGY. and fig. 51, ¢ and @), are usually more or less transversely- oblong or subquadrate, the two valves (as more or less in all Fig. 51.—Lower Silurian Brachiopods. a, Strophomena alternata, Cincinnati Group, America ; 6, Strophomena filitexta, Trenton and Cincinnati Groups, America; c, Orthis zestudinaria, Caradoc, Europe, and America; d@, a’, Orthis plicatella, Cincinnati Group, America; e, ¢’, e’, Leptena sericea, Llandeilo and Caradoc, Europe and Ame- rica. (After Meek, Hall, and the Author.) the Brachiopods) of unequal sizes, generally more or less con- vex, and marked with radiating ribs or lines. The valves of the shell are united to one another by teeth and sockets, and there is a straight hinge-line. The beaks are also separated by a distinct space (“‘hinge-area”’), formed in part by each valve, which is perforated by a triangular opening, through which, in the living condition, passed a muscular cord attach- ing the shell to some foreign object. The genus St/ophomena (fig. 50, d, and 51, a and 2) is very like Ortfzs in general char- acter ; but the shell 1s usually much flatter, one or other valve often being concave, the hinge-line is longer, and the aperture for the emission of the stalk of attachment is partially closed by a calcareous plate. In Leffena, again (fig. 51, e), the shell is like Strophomena in many respects, but generally compara- tively longer, often completely semicircular, and having one valve convex and the other valve concave. Amongst other genera of Brachiopods which are largely represented in the Lower Silurian rocks may be mentioned Lingua, Crantia, Discina, Trematis, Siphonotreta, Acrotreta, Rhynchonella, and Athyris ; but none of these can claim the importance to which the three previously-mentioned groups are entitled. The remaining Lower Silurian groups of JZo/lusca can be but briefly glanced at here. The Bivalves (Zamellibranchiata) find numerous representatives, belonging to such genera as THE | LOWER SILURIAN PERIOD. i Modiolopsis, Ctenodonta, Orthonota, Palearca, Lyrodesma, Am- bonychia, and Cleidophorus. ‘The Univalves (Gasteropoda) are also very numerous, the two most important genera being . Murchisonia (fig. 52) and Pleurotomaria. In both these groups the outer lip of the shell is notched ; but the shell in the former is elongated and turreted, whilst in the latter it is depressed. The curious oceanic Univalves known as the /eferopods are also very abundant, the principal forms belonging to Bed- lerophon and Maclurea. In the former (fig. 53) there is a symmetrical convoluted shell, like that of the Pearly Nautilus in shape, but without any internal partitions, and having the aperture of- ten expanded and notched behind. The species of Maclurea (fig. 54) are found both in North America and in Scotland, and are exclusively confined to the Lower Silurian period, so far as known. ‘They have the shell coiled into a flat spiral, the mouth being furnished with a very curious, thick, and solid lid or “opercu- _ Fa: 52-—4u- lum.” The Lower Silurian Preropods, or “‘Wing- Treen tne ed Snails,” are numerous, and belong principally (ane: Bille to the genera Zheca, Conularia, and Tentaculites, the last-mentioned of these often being extremely abundant in certain strata. Lastly, the Lower Silyrian Rocks have yielded a vast number Fig. 53.—Different views of Bellerophon Argo, Trenton Limestone, Canada. (After Billings.) of chambered shells, referable to animals which belong to the same great division as the Cuttle-fishes (the Cephalopoda), and of which the Pearly Nautilus is the only living representative at the present day. In this group of Cephalofods the animal possesses a well-developed external shell, which is divided into chambers by shelly partitions (“septa”). The animal lives in the last-formed and largest chamber of the shell, to T12 HISTORICAL PALZONTOLOGY. which it is organically connected by muscular attachments. The head is furnished with long muscular processes or ‘‘ arms,” Fig. 54.— Different views of laclurca crenulata, Quebec Group, Newfoundland. (After Billings.) : and can be protruded from the mouth of the shell at will, or again withdrawn within it. We learn, also, from the Pearly Nautilus, that these animals must have possessed two pairs of breathing organs or ‘gills ;” hence all these forms are grouped together under the name of the “ Tetrabranchiate ” Cephalo- pods (Gr. ¢etra, four; bragchia, gill). On the other hand, the ordinary Cuttle-fishes and Calamaries either possess an internal skeleton, or if they have an external shell, it is not chambered ; their “arms” are furnished with powerful organs of adhesion in the form of suckers ; and they possess only a single pair of gills. For this last reason they are termed the ‘“ Dibranchiate ” Cephalopods (Gr. dis, twice ; bragchia, gill). No trace of the true Cuttle-fishes has yet been found in Lower Silurian deposits; but the Tetrabranchiate group is represented by a great num- ber of forms, sometimes of great size. The principal Lower Silurian genus is the well-known and widely-distributed O7t/o- ceras (fig. 55). The shell in this genus agrees with that of the existing Pearly Nautilus, in consisting of numerous chambers separated by shelly partitions (or septa), the latter being per- forated by a tube which runs the whole length of the shell after the last chamber, and is known as the “siphuncle” (fig. 56, s). The last chamber formed is the largest, and in it the animal lives. The chambers behind this are apparently filled with some gas secreted by the animal itself; and these are sup- posed to act as a kind of float, enabling the creature to move with ease under the weight of its shell. The various air- chambers, though the sipbuncle passes through them, have no direct connection with one another ; and it is believed that the animal has the power of slightly altering its specific gravity, and thus ef rising or sinking in the water by driving additional fluid into the siphuncle or partially emptying it. The Ortho- THE LOWER SILURIAN PERIOD. I13 ceras further agrees with the Pearly Nautilus in the fact that the partitions or septa separating the different air-chambers are Fig. 55.—Fragment of Orthoceras crebri- septum, Cincinnati Group, North America, Fig. 56 —Restoration of Ovrthoceras, the shell being supposed to be divided ver- of the natural size. The lower figure isa section showing the air-chambers, and the form and position of the siphuncle. (After Billings.) tically, and only its upper part being shown. a, Arms; /, Muscular tube (‘‘funnel”) by which water is expelled from the mantle-chamber; c, Air-cham- bers ; s, Siphuncle. simple and smooth, concave in front and convex behind, and devoid of the elaborate lobation which they exhibit in the Ammonites ; whilst the siphuncle pierces the septa either in the centre or near it. In the Nautilus, however, the shell is coiled into a flat spiral; whereas in Orthoceras the shell is a straight, longer or shorter cone, tapering behind, and gradu- ally expanding towards its mouth in front. The chief objec- tions to the belief that the animal of the Or¢hoceras was essen- tially like that of the Pearly Nautilus are—the comparatively small size of the body-chamber, the often contracted aperture of the mouth, and the enormous size of some specimens of * This illustration is taken from a rough sketch made by the author many years ago, but he is unable to say from what original source it was copied. H 114 HISTORICAL PALAJONTOLOGY. the shell. Thus, some Ovrthocerata have been discovered measuring ten or twelve feet in length, with a diameter of a foot at the larger extremity. ‘These colossal dimensions cer- tainly make it difficult to imagine that the comparatively small body-chamber could have held an animal large enough to move a load so ponderous as its own shell. ‘To some, this difficulty has appeared so great that they prefer to believe that the Orthoceras did not live in its shell at all, but that its shell was an internal skeleton similar to what we shall find to exist in many of the true Cuttle-fishes. There is something to be said in favour of this view, but it would compel us to believe in the existence in Lower Silurian times of Cuttle-fishes fully equal in size to the giant “Kraken” of fable. It need only be added in this connection that the Lower Silurian rocks have yielded the remains of many other Tetrabranchiate Cephalo- pods besides Orthoceras. Some of these belong to Cyrtoceras, which only differs from Orthoceras in the bow-shaped form of the shell; others belong to Phragmoceras, Lituites, &c. ; and, lastly, we have true /Vaw?z/z, with their spiral shells, closely resembling the existing Pearly Nautilus. Whilst all the sub-kingdoms of the Invertebrate animals are represented in the Lower Silurian rocks, no traces of Verte- brate animals have ever been discovered in these ancient deposits, unless the so-called ‘‘Conodonts”’ found by Pander in vast numbers in strata of this age * in Russia should prove to be really of this nature. These problematical bodies are of microscopic size, and have the form of minute, conical, tooth- shaped spines, with sharp edges, and hollow at the base. Their original discoverer regarded them as the horny teeth of fishes allied to the Lampreys; but Owen came to the con- clusion that they probably belonged to Invertebrates. The recent investigation of a vast number of similar but slightly larger bodies, of very various forms, in the Carboniferous rocks of Ohio, has led Professor Newberry to the conclusion that these singular fossils really are, as Pander thought, the teeth of Cyclostomatous fishes. ‘The whole of this difficult question has thus been reopened, and we may yet have to record the first advent of Vertebrate animals in the Lower Silurian. * According to Pander, the ‘‘Conodonts” are found not only in the Lower Silurian beds, but also in the ‘‘ Ungulite Grit ” (Upper Cambrian), as well as in the Devonian and Carboniferous deposits of Russia. Should the Conodonts prove to be truly the remains of fishes, we should thus have to transfer the first appearance of Vertebrates to, at any rate, as early a period as the Upper Cambrian. THE UPPER SILURIAN PERIOD. PxS CHAPTERS es PHEPUPPER: SILURIAN BERIOD: Having now treated of the Lower Silurian period at consider- able length, it will not be necessary to discuss the succeeding group of the Upper Silurian in the same detail—the more so, as with a general change of sfecies the Upper Silurian animals belong for the most part to the same great ¢ypes as those which distinguish the Lower Silurian. As compared, also, as regards the total bulk of strata concerned, the thickness of the Upper Silurian is generally very much below that of the Lower Silurian, indicating that they represent a proportionately shorter period of time.’ In considering the general succession of the Upper Silurian beds, we shall, as before, select Wales and America as being two regions where these deposits are typically developed. In Wales and its borders the general succession of the Upper Silurian rocks may be taken to be as follows, in ascend- ing order (fig. 57) :— (1) The Base of the Upper Silurian series is constituted by a series of arenaceous beds, to which the name of “ May Hill Sandstone” was applied by Sedgwick. ‘These are succeeded by a series of greenish-grey or “pale- grey slates (‘‘’Tarannon Shales”), sometimes of great thickness ; and these two groups of beds together form what may be termed the “ May All Group” (Upper Llandovery of Murchison). ‘Though not very extensively developed in Britain, this zone is one very well marked by its fossils; and it corresponds with the ‘‘ Clinton Group” of North America, in which similar fossils occur. In South Wales this group is clearly unconformable to the highest member of the subjacent Lower Silurian (the Llandovery group); and there is reason to believe that a similar, though less con- spicuous, physical break occurs very generally between the base of the Upper and the summit of the Lower Silurian. (2) The Wenlock Group succeeds the May Hill group, and constitutes the middle member of the Upper Silurian. At its base it may have an irregular limestone (‘‘Woolhope Lime- stone”), and its summit may be formed bya similar but thicker calcareous deposit (‘Wenlock Limestone”); but the bulk of the group is made up of the argillaceous and shaly strata known as the “ Wenlock Shale.” In North Wales the Wenlock group is represented by a great accumulation of flaggy and gritty strata (the “ Denbighshire Flags and Grits”), and similar beds (the z1O HISTORICAL PALAZZONTOLOGY. “Coniston Flags” and “ Coniston Grits ”) take the same place in the north of England. (3) The Ludlow Group is the highest member of the Upper Silurian, and consists typically of a lower arenaceous and shaly series (the ‘‘Lower Ludlow Rock”) a middle calcareous member (the “ Aymestry Limestone”), and an upper shaly and sandy series (the ‘‘ Upper Ludlow Rock” and “‘ Downton Sand- stone”). At the summit, or close to the summit, of the Upper Ludlow, is a singular stratum only a few inches thick (vary- ing from an inch to a foot), which contains numerous remains of crustaceans and fishes, and is well known under the name of the ‘“‘bone-bed.” Finally, the Upper Ludlow rock graduates invariably into a series of red sandy deposits, which, when of a flaggy character, are known locally as the “ Tile-stones.” These beds are probably to be regarded as the highest member of the Upper Silurian; but they are sometimes looked upon as passage-beds into the Old Red Sandstone, or as the base of this formation. It is, in fact, apparently impossible to draw any actual line of demarcation between the Upper Silurian and the overlying deposits of the Devonian or Old Red Sandstone series. Both in Britain and in America the Lower Devonian beds repose with perfect conformity upon the highest Silurian beds, and the two formations appear to pass into one another by a gradual and imperceptible transition. The Upper Silurian strata of Britain vary from perhaps 3000 or 4000 feet in thickness up to 8000 or 10,000 feet. In North America the corresponding series, though also variable, is generally of much smaller thickness, and may be under 1000 feet. The general succession of the Upper Silurian deposits of North America is as follows :-— (1) Medina Sandstone—This constitutes the base of the Upper Silurian, and consists of sandy strata, singularly devoid of life, and passing below in some localities into a conglo- merate (‘Oneida Conglomerate”), which is stated to contain pebbles derived from the older beds, and which would thus indicate an unconformity between the Upper and Lower Silurian. (2) Clinton Group.— Above the Medina sandstone are beds of sandstone and shale, sometimes with calcareous bands, which constitute what is known as the “ Clinton Group.” The Medina and Clinton groups are undoubtedly the equivalent of the “ May Hill Group” of Britain, as shown by the identity of their fossils. THE. UPPER SILURIAN PERIOD. EZ GENERALISED SECTION OF THE UPPER SILURIAN STRATA OF WALES AND SHROPSHIRE. Fig. 57. Cie Ose, wie. o JO, © i { Base of Old Red Sand- St a a Ee (stone: im 2 Tile-stones. 4 oO 2 Upper Ludlow Rock. a Aymestry Limestone. 4 Lower Ludlow Rock. = Wenlock Limestone. e O Wenlock Shale (Denbigh- 4 shire Flags and Grits of Q North Wales). A SI = Woolhope Limestone. Tarannon Shales. so a ee “fs 3 pay : tee = ; See Ae St May Hill Sandstone. i ee ay Pea er = er °o . Be Ported he mea ee. May- Hit GROUP Llandovery Rocks. (3) Magara Group.—This group consists typically of a series of argillaceous beds (‘‘ Niagara Shale”) capped by limestones (‘‘ Niagara Limestone”’); and the name of the group is derived from the fact that it is over limestones of this age that the Niagara river is precipitated to form the great Falls. In places the Niagara group is wholly calcareous, and it is continued upwards into a series of marls and sand- stones, with beds of salt and masses of gypsum (the “Salina Group”), or into a series of magnesian limestones (“ Guelph Limestones”). The Niagara group, as a whole, corresponds unequivocally with the Wenlock group of Britain. (4) Lower Helderberg Group.—The Upper Silurian period in North America was terminated by the deposition of a series of calcareous beds, which derive the name of “ Lower Helder- berg” from the Helderberg mountains, south of Albany, and 118 HISTORICAL PALZAONTOLOGY. which are divided into several zones, capable of recognition by their fossils, and known by local names (Tentaculite Lime- stone, Water-lime, Lower Pentamerus Limestone, Delthyris Shaly Limestone, and Upper Pentamerus Limestone). As a whole, this series may be regarded as the equivalent of the Ludlow group of Britain, though it is difficult to establish any precise parallelism. ‘The summit of the Lower Helderberg group is constituted by a coarse-grained sandstone (the “ Oris- kany Sandstone”), replete with organic remains, which have to a large extent a Silurian facies. Opinions differ as to whether this sandstone is to be regarded as the highest bed of the Upper Silurian or the base of the Devonian. We thus see that in America, as in Britain, no other line than an artificial one can be drawn between the Upper Silurian and the overlying Devonian. As regards the “fe of the Upper Silurian period, we have, as before, a number of so-called ‘ Fucoids,” the true vegetable nature of which is in many instances beyond doubt. In addi- tion to these, however, we meet for the first time, in deposits of this age, with the remains of genuine land-plants, though our knowledge of these 1s still too scanty to enable us to con- struct any detailed picture of the terrestrial vegetation of the period. Some of these remains indicate the existence of the remarkable genus Lepidodendron—a genus which played a part of great importance in the forests of the Devonian and Carbon- iferous periods, and which may be regarded as a gigantic and extinct type of the Club-mosses (Lycopodiacee). _ Near the summit of the Ludlow formation in Britain there have also been found beds charged with numerous small globular bodies, which Dr Hooker has shown to be the seed-vessels or “ spor- angia” of Club-mosses. Principal Dawson further states that he has seen in the same formation fragments of wood with the structure of the singular Devonian Conifer known as /Profo- taxites. Lastly, the same distinguished observer has described from the Upper Silurian of North America the remains of the singular land-plants belonging to the genus Psz/ophyton, which will be referred to at greater length hereafter. The marine life of the Upper Silurian is in the main con- stituted by types of animals similar to those characterising the Lower Silurian, though for the most part belonging to different species. The Protozoans are represented principally by S¢ro- matopora and Ischadites, along with a number of undoubted sponges (such as Amphispongia, Astreospongia, Astylospongia, and Paleomanon). Amongst the Celenterates, we find the old group of Graf- tolites now verging on extinction. Individuals still remain THE UPPER SILURSAN, PERIOD. Ii9 numerous, but the variety of generic and specific types has now become greatly reduced. All the branching and complex forms of the Arenig, the twin-Grap- tolites and Duzcranograpti of the Llandeilo, and the double-celled Diplograptt and Clhmacograpti of the Bala group, have now disap- peared. In their place we have the singular Refzolzes, with its curi- ously-reticulated skeleton; and seve- ral species of the single-celled genus Monograptus, of which a character- ‘istic species (JZ. priodon) is here figured. If we remove from this group the plant-like Ductyoneme, which are still present, and which survive into the Devonian, no known species of Gvaftolite has hitherto been detected in strata higher in geological position than the Ludlow. This, therefore, pre- sents us with the first instance we have as yet met with of the total disappearance and extinction of a great and important series of or- ganic forms. The Corals are very numerously represented in the Upper Silurian rocks, some of the limestones (such as the Wenlock Limestone) being often largely composed of the skeletons of these animals. Almost all the known forms of this period belong to the two great divisions of the Rugose and Tabulate corals, the former being represented by species of Zaphrentis, Omphyma, Cystiphyllum, Strombodes, Acervularia, Cyathophylum, Fig. 58.—A, IMWonograptus prio- don, slightly enlarged. B, Frag- ment of the same viewed from behind. C, Fragment of the same viewed in front, showing the mouths of the cellules. D, Cross-section of the same. From the Wenlock Group (Coniston Flags of the North of England). (Original.) SC whilst the latter belong principally to the genera Savosites, Chetetes, Halysites, Syringopora, Heliolites, and Plasmopora. Amongst the Awgosa, the first appearance of the great and important genus Cyathophyllum, so characteristic of the Palz- OzoOic period, is to; be pred : and amongst the Zadulata we have similarly the first appearance, in force at any rate, of the widely-spread genus Savosites — the “ Honeycomb- corals.” The ‘Chain- corals” (Halysites), figured below (fig. 59), are also very common examples of the Tabulate corals during this period, though they occur likewise in the Lower Silurian. 120 HISTORICAL PALAZZONTOLOGY. Amongst the £chinodermata, all those orders which have hard parts capable of ready preservation are more or less Shoovesceut Gegerecrvcong 1 Fig. 59.—a, Halysites catenularia, small variety, of the natural size ; 4, Fragment of a large variety of the same, of the natural size; c, Fragment of limestone with the tubes of Halysites agglomerata, of the natural size; d, Vertical section of two tubes of the same, showing the tabulz, enlarged. Niagara Limestone (Wenlock), Canada. (Original.) largely represented. We have no trace of the Holothurians or Sea-cucumbers ; but this is not surprising, as the record of the past is throughout almost silent as to the former existence of these soft-bodied creatures, the scattered plates and spicules in their skin offering a very uncertain chance of preservation in the fossil condition. The Sea-urchins (Zchznoids) are said to be represented by examples of the old genus Padechinus. The Star-fishes (Asteroids) and the Brittle-stars (Ophiurozds) are, comparatively speaking, largely represented ; the former by species of Palasterina (fig. 60), Paleaster (fig. 60), Paleo- coma (fig. 60), Petraster, Glyptaster, and Lepidaster—and the latter by species of Protaster (fig. 61), Paleodiscus, Acroura, and Lucladia. The singular Cystideans, or ‘“‘ Globe Crinoids,” with their globular or ovate, tesselated bodies (fig. 46, A, C, D,), are also not uncommon in the Upper Silurian ; and if they do not become finally extinct here, they certainly survive the close of this period by but a very brief time. By far the most im- portant, however, of the Upper Silurian Echinoderms, are the Sea-liles or Crizoids. ‘The limestones of this period are often largely composed of the fragmentary columns and detached THE UPPER SILURIAN PERIOD. [25 plates of these creatures, and some of them (such as the Wen- lock Limestone of Dudley) have yielded perhaps the most NY 7/7 ZN Fig. 60.—Upper Silurian Star-fishes. 1, Palasterina primeva, Lower Ludlow ; 2, Paleaster Ruthveni, Lower Ludlow; 3, Paleocoma Colvini, Lower Ludlow. (After Salter.) exquisitely-preserved examples of this group with which we are as yet acquainted. However varied in their forms, these _ Fig. 61.—A, Protaster Sedgwickii, showing the disc and_bases of the arms ; B, Por- tion of an arm, greatly enlarged. Lower Ludlow. (After Salter.) beautiful organisms consist of a globular, ovate, or pear-shaped body (the ‘calyx”), supported upon a longer or shorter jointed stem (or “ column”). The body is covered externally with an armour of closely-fitting calcareous plates (fig. 62), and its upper surface is protected by similar but smaller plates more loosely connected by a leathery integument. From the upper surface of the body, round its margin, springs a series of longer or shorter flexible processes, composed of innu- merable calcareous joints or pieces, movably united with one I22 HISTORICAL PALAONTOLOGY. another. The arms are typically five in number; but they generally subdivide at least once, sometimes twice, and they nee. \ CL) Pe )s} 2 i) Gag vidi (| meee’ yt) 2) 3) BS, ris(= a i i PU ise a Binge Gs STARR (TTe] [7 jag Hele Dp. = isi, Tee : Fig. 62.—Upper Silurian Crinoids. a, Calyx and arms of Zucalyptocrinus polydacty- Zus, Wenlock Limestone ; 6, /chthyocrinus levis, Niagara Limestone, America; ¢, Taxocrinus tuberculatus, Wenlock Limestone. (After M‘Coy and Hall.) are furnished with similar but more slender lateral branches or ‘ pinnules,” thus giving rise to a crown of delicate feathery plumes. The “column” is the stem by which the animal is attached permanently to the bottom of the sea; and it is com- posed of numerous separate plates, so jointed together that whilst the amount of movement between any two pieces must be very limited, the entire column acquires more or less flexi- bility, allowing the organism as a whole to wave backwards and forwards on its stalk. Into the exquisite mznwtie of structure by which the innumerable parts entering into the composition of a single Crinoid are adapted for their proper purposes in the economy of the animal, it is impossible to enter here. No period, as before said, has yielded examples of greater beauty than the Upper Silurian, the principal genera represented being Cyathocrinus, Platycrinus, Marsupiocrinus, Taxocrinus, Lucalyptocrinus, Ichthyocrinus, Mariacrinus, FPeriechocrinus, Glyptocrinus, Crotalocrinus, and Ldriocrinus. The tracks and burrows of Annelides are as abundant in the Upper Silurian strata as in older deposits, and have just as commonly been regarded as plants. ‘The most abundant forms are the cylindrical, twisted bodies (Planolites), which are THE UPPER SILURIAN PERIOD. 123 so frequently found on the surfaces of sandy beds, and which have been described as the stems of sea-weeds. ‘These fossils (fig. 63), however, can be nothing more, in most cases, than Fig. 63.—Planolites vulgaris, the filled-up burrows of a marine worm. Upper Silurian (Clinton Group), Canada. (Original.) the filled-up burrows of marine worms resembling the living Lob-worms. There are also various remains which belong to the group of the tube-inhabiting Annelides (Zudicola). Of this nature are the tubes of Serpudlites and Cornulites, and the little spiral discs of Spzvorbis Lewirsit. . Amongst the Articulates, we still meet only with the remains of Crustaceans. Besides the little bivalved Ostracoda—which here are occasionally found of the size of beans—and various Phyllopods of different kinds, we have an abundance of Z7z/o- bites. These last-mentioned ancient types, however, are now beginning to show signs of decadence ; and though still indi- vidually numerous, there is a great diminution in the number of generic types. Many of the old genera, which flourished so abundantly in Lower Silurian seas, have now died out; and the group is represented chiefly by species of Cheirurus, Encrinurus, Harpes, Proetus, Lichas, Acidaspis, Ilenus, Caly- mene, Homalonotus, and Phacops—the last of these, one of the 124 HISTORICAL PALAZZONTOLOGY. highest and most beautiful of the groups of Trilobites, attaining here its maximum of development. In the annexed illustra- tion (fig. 64) some of the characteristic Upper Silurian Trilo- Fig. 64.—Upper Silurian Trilobites. a, Chetrurus bineucronatus, Wenlock and Cara- doc; 6, Phacops longicaudatus, Wenlock, Britain, and America; c, Phacofs Downingia, Wenlock and Ludlow; ad, Harfes ungula, Upper Silurian, Bohemia. (After Salter and Barrande.) bites are represented—all, however, belonging to genera which have their commencement in the Lower Silurian period. In addition to the above, the Ludlow rocks of Britain and the Lower Helderberg beds of North America have yielded the remains of certain singular Crustaceans belonging to the extinct order of the Lurypterida. Some of these wonderful forms are not remarkable for their size; but others, such as Prerygotus Anglicus (fig. 65), attain a length of six feet or more, and may fairly be considered as the giants of their class. The Eurypterids are most nearly allied to the existing King-crabs (Zzmulz), and have the anterior end of the body covered with a great head-shield, carrying two pairs of eyes, the one simple and the other compound. ‘The feelers are converted into pincers, whilst the last pair of limbs have their bases covered with spiny teeth so as to act as jaws, and are flattened and widened out towards their extremities so as to officiate as swimming-paddles. The hinder extremity of the body is com- posed of thirteen rings, which have no legs attached to them ; and the last segment of the tail is either a flattened plate or a THE, UPPER SILURIAN) PERIOD. 125 narrow, sword-shaped spine. Fragments of the skeleton are easily recognised by the peculiar scale-like markings with which the surface is adorned, and which look not at all unlike the scales of a fish. ‘The most fam- ous locality for these great Crus- taceans 1s Lesmahagow, in Lan- arkshire, where many different species have been found. ‘The true King-crabs (Zzz/z) of exist- ing seas also appear to have been represented by at least one form (Weolimulus) in the Upper Silu- rian. Coming to the A/ollusca, we note the occurrence of the same great groups as in the Lower Silurian. Amongst the Sea- mosses (/olyzoa), we have the ancient Lace-corals (/enestella and fefepora), with the nearly- allied Glauconome, and species of Ptilodiciya (fig. 66) ; whilst many forms often referred here may probably have to be transferred to the Corals, just as some so- called Corals will ultimately be Fig. viewed from the under side, reduced 65.— Pterygotus Anglicus, in size, and restored. cc, The feelers (antennz), terminating in nipping- removed to the present group. The Brachiopods continued to flourish during the Upper Silurian period in immense num- claws ; 0 0, Eyes ; 7 #, Three pairs of jointed limbs, with pointed extremi- ties ; 72 2, Swimming-paddles, the bases of which are spiny and act as jaws. Upper Silurian, Lanarkshire. (After ; Henry Woodward.) bers and under a greatly in- creased variety of forms. The three prominent Lower Silurian genera Orthis, Strophomena, and Leftena are still well represented, though they have lost their former pre- eminence. Amongst the numerous types which have now come upon the scene for the first time, or which have now a special development, are Spiérifera and Pentamerus. In the first of these (fig. 69, 4, c), one of the valves of the shell (the dorsal) is furnished in its interior with a pair of great calca- reous spires, which served for the support of the long and fringed fleshy processes or “ arms” which were attached to the sides of the mouth.* In the genus Pentamerus (fig. 70) the * In all the Lamp-shells the mouth is provided with two long fleshy organs, which carry delicate filaments on their sides, and which are 126 HISTORICAL PALAONTOLOGY. shell is curiously subdivided in its interior by calcareous plates. The /entameri commenced their existence at the very Fig. 66.—Upper Silurian Polyzoa. 1, Fan-shaped frond of Rhixofora verrucosa; 1a, Portion of the surface of the same, enlarged; 2 and 2a, Phenopora enstformts, of the * natural size and enlarged; 3 and 3a, Helofora fragilis, of the natural size and en- larged ; 4 and 4a, Ptilodictya rarifora, of the natural size and enlarged. The speci- mens are all from the Clinton Formation (May Hill Group) of Canada. (Original.) close of the Lower Silurian (Llandovery), and survived to the close of the Upper Silurian; but they are specially character- istic of the May Hill and Wenlock groups, both in Britain and in other regions. One species, Pentamerus galeatus, is common to Sweden, Britain, and America. Amongst the remaining Upper Silurian Brachiopods are the extraordinary usually coiled into a spiral. These organs are known as the ‘‘arms,” and it is from their presence that the name of ‘‘ Brachiopoda” is derived (Gr. drachion, arm ; podes, feet). In some cases the arms are merely coiled away within the shell, without any support; but in other cases they are carried upon a more or less elaborate shelly loop, often spoken of as the ‘‘carriage-spring apparatus.” In the Sfirifers, and in other ancient genera, this apparatus is coiled up into a complicated spiral (fig. 67). It Fig. 67.—Spirifera hysterica. The right-hand figure shows the interior of the dorsal valve, with the calcareous spires for the support of the arms. is these ‘‘arms,” with or without the supporting loops or spires, which serve as one of the special characters distinguishing the Lrachiopods from the true Bivalves (Lamellibranchiata). THE UPPER: SILURIAN PERIOD. 127 Trimerellids ; the old and at the same time modern Zingwle, Discine, and Cranieé ; together with many species of Atrypa Fig. 68.— Upper Silurian Brachiopods. aa’, Lefptocelia plano-convexa, Clinton Group, America; 68’, Rhynchonella neglecta, Clinton Group, America; c, Rhynchonella cuneata, Niagara Group, America, and Wenlock Group, Britain; @ a’, Orthis elegan- zula, Llandeilo to Ludlow, America and Europe; e e’, Atrypa hemispherica, Clinton Group, America, and Llandovery and May Hill Groups, Britain; /_/’, Atvxyfa congesta, Clinton Group, America ; ¢ g’, Orthis Davidsoni, Clinton Group, America. (After Hall, Billings, and the Author.) (fig. 68, e), Leptocelia (fig. 68, a), Rhynchonella (fig. 68, 4, ¢), Meristella (fig. 69, a, ¢, f), Athyris, Retzia, Chonetes, &c: Niagara Group, America. (After Hall, Billings, and the Author.) The higher groups of the A/o/usca are also largely repre- sented in the Upper Silurian. Apart from some singular types, Res: HISTORICAL PALASONTOLOGY. such as the huge and thick-shelled AZega/omi of the American Wenlock formation, the Bivalves (Zamellibranchiata) present Fig. 70.—Pentamerus Knightiz. Wenlock and Ludlow. The right-hand figure shows the internal partitions of the shell. little of special interest ; for though sufficiently numerous, they are rarely well preserved, and their true affinities are often un- certain. Amongst the most characteristic genera of this period may be mentioned Cardvo/a (fig. 71, A and C) and Prerinea (fig. Fig. 71.—Upper Silurian Bivalves. A, Cardiola interrupta, Wenlock and Ludlow; B, Pterinea subfalcata, Wenlock; C, Cardiola fibrosa, Ludlow. (After Salter and M ‘Coy.) 71, B), though the latter survives to a much later date. The Univalves (Gasteropoda) are very numerous, and a few charac- teristic forms are here figured (fig. 72). Of these, no genus is perhaps more characteristic than Lwomphalus (fig. 72, 6), with its flat discoidal shell, coiled up into an oblique spiral, and deeply hollowed out on one side; but examples of this group are both of older and of more modern date. Another very extensive genus, especially in America, is Platyceras (fig. 72, a and f), with its thin fragile shell—often hardly coiled up at all—its minute spire, and its widely-expanded, often sinuated mouth. The British Acroculie should probably be placed here, and the group has with reason been regarded as allied to the Violet-snails (Zanthina) of the open Atlantic. The THE UPPER SILURIAN PERIOD. 129 species of FPlatyostoma (fig. 72, 2%) also belong to the same family ; and the entire group is continued throughout the Devonian into the Carboniferous. Amongst other well-known Upper Silurian Gasteropods are species of the genera Holopea Fig. 72.—Upper Silurian Gasteropods. a, Platyceras ventricosum, Lower Helder- berg, America; 4, Exonephalus discors, Wenlock, Britain; c, Holopella obsoleta, Lud- low, Britain; d, Platyschisma helicites, Upper Ludlow, Britain; e, Holopella gracilior, Wenlock, Britain; 7, Platyceras multisinuatum, Lower Helderberg, America; g, Holc- pea subconica, Lower Helderberg, America; , 2’, Platyostoma Niagarense, Niagara _ Group, America. (After Hall, M‘Coy, and Salter.) (fig. 72, g), Holopella (fig. 72, ¢), Platyschisma (fig. 72, @), Cyclonema, Pleurotomaria, Murchisonia, Trochonema, &c. The oceanic Univalves (/Zeferopods) are rep- resented mainly by species of Ledlero- phon; and the Winged Snails, or Prero- pods, can still boast of the gigantic. Zhece and Conulari@g, which characterise yet older deposits. The commonest genus of Preropoda, however, is Tentaculites (fig. 73), which clearly belongs here, though it has commonly been regarded as the tube of an Annelide. The shell in this group is a conical tube, usually adorned with prominent transverse rings, and _ Fig 73.—Tentaculites or- : : : natus. Upper Silurian of often with finer transverse or longitudi- Europeand North America. nal striz as well; and many beds of the Upper Silurian exhibit myriads of such tubes scattered promis- cuously over their surfaces. 130 HISTORICAL PALAEONTOLOGY. The last and highest group of the Ao//usca—that of the Cephalopoda —is still represented only by TZetrabranchiate forms; but the abundance and variety of these is almost beyond belief. Many hundreds of different species are known, chiefly belonging to the straight Orthoceratites, but the slightly- curved Cyrtoceras is only little less common. There are also numerous forms of the genera Phragmoceras, Ascoceras, Gyro- ceras, Lituites, and Vautilus. Here, also, are the first-known species of the genus Gomiatites—a group which attains con- siderable importance in later deposits, and which is to be regarded as the precursor of the Ammonites of the Secondary period. Finally, we find ourselves for the first time called upon to consider the remains of undoubted vertebrate animals, in the form of fishes. The oldest of these remains, so far as yet known, are found in the Lower Ludlow rocks, and they con- sist of the bony head-shields or bucklers of certain singular armoured fishes belong- ing to the group of the Ganoids, repre- sented at the present day by the Stur- geons, the Gar-pikes of North America, and a few other less familiar forms. The principal Upper Silurian genus of these is FPteraspis, and the annexed illustration (fig. 74) will give some idea of the extraordi- nary form of the shield covering the head in these ancient fishes. ‘The remarkable Fig. 74.—Head-shield stratum near the top of the Ludlow for- iiian Somes Cane mation known as the ‘ bone-bed” has Murchison.) also yielded the remains of shark-like fishes. Some of these, for which the name of Onchus has been proposed, are in the form of com- pressed, slightly-curved spines (fig. 75, A), which would appear Fig. 75.—A, Spine of Onchus tenuistriatus ; B, Shagreen-scales of Thelodus. Both “front "the ‘bone-bed ” of the Upper Ludlow rocks. (After Murchison. ) to be of the nature of the strong defensive spines implanted in front of certain of the fins in many living fishes. Besides" these, have been found fragments of prickly skin or shagreen (Sphagodus), along with minute cushion-shaped bodies (Zheo- THE) UPPER SILURIAN PERIOD. 131 dus, fig. 75, B), which are doubtless the bony scales of some fish resembling the modern Dog-fishes. As the above mentioned remains belong to two distinct, and at the same .time highly- organised, groups of the fishes, it is hardly likely that we are really presented here with the first examples of this great class. On the contrary, whether the so-called ‘‘ Conodonts” should prove to be the teeth of fishes or not, we are justified in ex- pecting that unequivocal remains of this group of animals will still be found in the Lower Silurian. It is interesting, also, to note that the first appearance of fishes—the lowest class of vertebrate animals—so far as known to us at present, does not take place until after all the great sub-kingdoms of invertebrates have been long in existence; and there is no reason for think- ing that future discoveries will materially affect the relative order of succession thus indicated. LITERATURE. From the vast and daily-increasing mass of Silurian literature, it is im- possible to do more than select a small number of works which have a classical and historical interest to the English-speaking geologist, or which embody researches on special groups of Silurian animals—anything like an enumeration of all the works and papers on this subject being wholly out of the question. Apart, therefore, from numerous and in many cases extremely important memoirs, by various well-known observers, both at home and abroad, the following are some of the more weighty works to which the student may refer in investigating the physical characters and succession of the Silurian strata and their fossil contents :— (1) ‘Siluria.? Sir Roderick Murchison. (2) ‘Geology of Russia in Europe.’ Murchison (with M. de Verneuil and Count von Keyserling). (3) ‘ Bassin Silurien de Bohéme Centrale.’ Barrande. (4) ‘Introduction to the Catalogue of British Paleozoic Fossils in the Woodwardian Museum of Cambridge.’ Sedgwick. (5) ‘Die Urwelt Russlands.’ Eichwald. (6) ‘Report on the Geology of Londonderry, Tyrone,’ &c. Portlock. » (7) ‘*Geology of North Wales”—* Mem. Geol. Survey of Great Britain,’ vol. iii. Ramsay. (8) ‘ Geology of Canada,’ 1863, Sir W. E. Logan ; and the ‘ Reports of Progress of the Geological Survey’ since 1863. (9) ‘ Memoirs of the Geological Survey of Great Britain.’ (10) ‘Reports of the Geological Surveys of the States of New York, Illinois, Ohio, Iowa, Michigan, Vermont, Wisconsin, Minne- sota,’ &c. By Emmons, Hall, Worthen, Meek, Newberry, Orton, Winchell, Dale Owen, &c. (11) ‘ Thesaurus Siluricus.’ Bigsby. ) ‘British Palzeozoic Fossils.” M‘Coy. (13) ‘ Synopsis of the Silurian Fossils of Ireland,’ M‘Coy. ) ‘* Appendix to the Geology of North Wales ”—‘ Mem. Geol. Survey,’ vol. iii, Salter. 132 (15) (16 (17 (18 (19) (20) (21) (22) ——— ~_—— HISTORICAL PALZONTOLOGY. ‘Catalogue of the Cambrian and Silurian Fossils in the Woodward- ian Museum of Cambridge.’ Salter. ‘ Characteristic British Fossils.’ Baily. ‘Catalogue of British Fossils.’ Morris. * Paleozoic Fossils of Canada.’ Billings. ‘Decades of the Geological Survey of Canada.’ Billings, Salter, Rupert Jones. ‘ Decades of the Geological Survey of Great Britain.’ Salter, Edward Forbes. ‘ Paleontology of New York,’ vols. i.-iii. Hall. ‘ Paleontology of Illinois.’ Meek and Worthen. ) ‘Paleontology of Ohio.’ Meek, Hall, Whitfield, Nicholson. ‘Silurian Fauna of West Tennessee’ (Silurische Fauna des West- lichen Tennessee). Ferdinand Rcemer. ‘Reports on the State Cabinet of New York.’ Hall. ‘ Lethzea Geognostica.” Bronn. ‘Index Palzontologicus.’ Bronn. ‘ Lethzea Rossica.’ Eichwald. ‘Lethzea Suecica.’ Hisinger. ‘ Palzontologica Suecica.’ Angelin. ‘ Petrefacta Germaniz.’ Goldfuss. ‘Versteinerungen der Grauwacken-Formation in Sachsen.’ Geinitz, ‘ Organisation of Trilobites’ (Ray Society). Burmeister. ‘Monograph of the British Trilobites’ (Paleeontographical Society). Salter. ‘ Monograph of the British Merostomata’ (Paleeontographical Society). Henry Woodward. Monograph of British Brachiopoda’ (Palzeontographical Society). Thomas Davidson. ‘Graptolites of the Quebec Group.’ James Hall. ‘Monograph of the British Graptolitidee.’ Nicholson. ‘Monographs on the Trilobites, Pteropods, Cephalopods, Grapto- lites,’ &c. Extracted from the ‘Systeme Silurien du Centre de la Bohéme.’ Barrande. ‘ Polypiers Fossiles des Terrains Paleozoiques,’ and ‘ Monograph of the British Corals’ (Palzontographical Society), Milne Ed- wards and Jules Haime. CEL AP WE Roots THE DEVONIAN AND OLD RED SANDSTONE PERIOD. Between the summit of the Ludlow formation and the strata which are universally admitted to belong to the Carboniferous DEVONIAN AND OLD RED PERIOD. 133 series is a great system of deposits, to which the name of “ Old Red Sandstone” was originally applied, to distinguish them from certain arenaceous strata which lie above the coal (“ New Red Sandstone”). The Old Red Sandstone, properly so called, was originally described and investigated as occurring in Scotland and in South Wales and its borders ; and similar strata occur in the south of Ireland. Subsequently it was discovered that sediments of a different mineral nature, and containing different organic remains, intervened between the Silurian and the Carboniferous rocks on the continent of Eu- rope, and strata with similar paleontological characters to these were found occupying a considerable area in Devonshire. The name of “‘ Devonian” was applied to these deposits ; and this title, by common usage, has come to be regarded as synony- mous with the name of ‘Old Red Sandstone.” Lastly, a magnificent series of deposits, containing marine fossils, and undoubtedly equivalent to the true “ Devonian” of Devon- shire, Rhenish Prussia, Belgium, and France, is found to inter- vene in North America between the summit of the Silurian and the base of the Carboniferous rocks. Much difficulty has been felt in correlating the true ‘‘ Devon- ian Rocks” with the typical “Old Red Sandstone”—this difh- culty arising from the fact that though both formations are fossiliferous, the peculiar fossils of each have only been rarely and partially found associated together. The characteristic crustaceans and many of the characteristic fishes of the Old Red are wanting in the Devonian; whilst the corals and marine shells of the latter do not occur in the former. It is impossible here to enter into any discussion as to the merits of the controversy to which this difficulty has given origin. No one, however, can doubt the importance and reality of ‘the Devonian series as an independent system of rocks to be in- tercalated in point of time between the Silurian and the Car- boniferous. The want of agreement, both lthologically and palzontologically, between the Devonian and the Old Red, can be explained by supposing that these two formations, though wholly or in great part contemporaneous, and therefore strict equivalents, represent deposits in two different geographi- cal areas, laid down under different conditions. On this view, the typical Devonian rocks of Europe, Britain, and North America are the deep-sea deposits of the Devonian period, or, at any rate, are genuine marine sediments formed far from land. On the other hand, the ‘Old Red Sandstone” of Britain and the corresponding ‘‘Gaspé Group” of Eastern 134 HISTORICAL’ PALAIONTOLOGY. Canada represent the shallow-water shore-deposits of the same period. In fact, the former of these last-mentioned de- posits contains no fossils which can be asserted positively to be marine (unless the Eurypterids be considered so) ; and it is even conceivable that it represents the sediments of an inland sea. Accepting this explanation in the meanwhile, we may very briefly consider the general succession of the deposits of this period in Scotland, in Devonshire, and in North America. In Scotland the “Old Red” forms a great series of arena- ceous and conglomeratic strata, attaining a thickness of many thousands of feet, and divisible into three groups. Of these, the Lower Old Red Sandstone reposes with perfect conform- ity upon the highest beds of the Upper Silurian, the two for- mations being almost inseparably united by an intermediate series of “ passage-beds.” In mineral nature this group con- sists principally of massive conglomerates, sandstones, shales, and concretionary limestones ; and its fossils consist chiefly of large crustaceans belonging to the family of the Luryfterids, fishes, and plants. The J@ddle Old Red Sandstone consists ot flagstones, bituminous shales, and conglomerates, sometimes with irregular calcareous bands ; and its fossils are principally fishes and plants. It may be wholly wanting, when the Upger Old Red seems to repose unconformably upon the lower divi- sion of the series. The Upper Old Red Sandstone consists of conglomerates and grits, along with a great series of red and yellow sandstones—the fossils, as before, being fishes and re- mains of plants. The Upper Old Red graduates upwards conformably into the Carboniferous series. The Devonian rocks of Devonshire are likewise divisible into a lower, middle, and upper division. The Lower Devonian or Lynton Group consists of red and purple sand- stones, with marine fossils, corresponding to the ‘Spirifer Sandstein ” of Germany, and to the arenaceous deposits (Scho- harie and Cauda-Galli Grits) at the base of the American Devonian. The J@iddle Devonian or Lifracombe Group consists of sandstones and flags, with calcareous slates and crystalline limestones, containing many corals. It corresponds with the great “Eifel Limestone” of the Continent, and, in a general way, with the Corniferous Limestone and Hamilton group of North America. The Upper Devonian or Pilton Group, lastly, consists of sandstones and calcareous shales which correspond with the ‘‘Clymenia Limestone” and “ Cypridina Shales” of the Continent, and with the Chemung and Portage groups of DEVONIAN AND OLD RED PERIOD. 135 North America. It seems quite possible, also, that the so- called ‘‘ Carboniferous Slates” of Ireland correspond with this group, and that the former would be more properly re- garded as forming the summit of the Devonian than the base of the Carboniferous. In no country in the world, probably, is there a finer or more complete exposition of the strata intervening be- tween the Silurian and Carboniferous deposits than in the United States. The following are the main subdivisions of the Devonian rocks in the State of New York, where the series may be regarded as being typically developed fig. 67) :— : (1) Cauda-Galli Grit and Schoharie Grit.—Considering the “Oriskany Sandstone” as the summit of the Upper Silurian, the base of the Devonian is constituted by the arenaceous deposits known by the above names, which rest quite conform- ably upon the Silurian, and which represent the Lower Devonian of Devonshire. The Cauda-Galli Grit is so called from the abundance of a peculiar spiral fossil (Spzrophyton cauda-Galli), which is of common occurrence in the Carbon- iferous rocks of Britain, and is supposed to be the remains of a sea-weed. (2) The Corniferous or Upper Helderberg Limestone. — A series of limestones usually charged with considerabie quan- tities of siliceous matter in the shape of hornstone or chert (Lat. cornu, horn). ‘The thickness of this group rarely exceeds 300 feet; but it is replete with fossils, more especially with the remains of corals. The Corniferous Limestone is the equivalent of the coral-bearing limestones of the Middle De- vonian of Devonshire and the great ‘ Eifel Limestone” of Germany. (3) The Hamilton Group—consisting of shales at the base (‘‘ Marcellus shales”); flags, shales, and impure limestones (‘Hamilton beds”) in the middle; and again a series of shales (‘Genesee Slates”) at the top. The thickness of this group varies from 200 to 1200 feet, and it is richly charged with marine fossils. (4) The Portage Group.—A great series of shales, flags, and shaly sandstones, with few fossils. (5) The Chemung Group—Another great series of sand- stones and shales, but with many fossils. The Portage and Chemung groups may be regarded as corresponding with the Upper Devonian of Devonshire. The Chemung beds are succeeded by a great series of red sandstones and shales—the 136 HISTORICAL PALAZZAONTOLOGY. “* Catskill Group”—which pass conformably upwards into the Carboniferous, and which may perhaps be regarded as the equivalent of the great sandstones of the Upper Old Red in Scotland. Throughout the entire series of Devonian deposits in North America no unconformability or physical break of any kind has hitherto been detected ; nor is there any marked interrup- tion to the-current of life, though each subdivision of the series has its own fossils. No completely natural line can thus be indicated, dividing the Devonian in this region from the Silu- rian on the one hand, and the Carboniferous on the other hand. At the same time, there is the most ample evidence, both stratigraphical and paleontological, as to the complete independence of the American Devonian series as a distinct life-system between the older Silurian and the later Carbon- iferous. The subjoined section (fig. 76) shows diagrammati- cally the general succession of the Devonian rocks of North America. As regards the “/e of the Devonian period, we are now acquainted with a large and abundant terrestrial /7ora—this being the first time that we have met with a land vegetation capable of reconstruction in any fulness. By the researches of Goeppert, Unger, Dawson, Carruthers, and other botanists, a knowledge has been acquired of a large number of Devonian plants, only a few of which can be noticed here. As might have been anticipated, the greater number of the vegetable remains of this period have been obtained from such shallow- water deposits as the Old Red Sandstone proper and the Gaspe series of North America, and few traces of plant-life occur in the strictly marine sediments. Apart from numerous remains, mostly of a problematical nature, referred to the comprehensive group of the Sea-weeds, a large number of Ferns have now been recognised, some being of the ordinary plant-like type (Pecopterts, Neuropteris, Alethopteris, Sphenopteris, &c.), whilst others belong to the gigantic group of the “ Tree - ferns” (Psaronius, Caulopteris, &c.) Besides these there is an abun- dant development of the singular extinct types of the Zefzdo- dendroids, the Sigillarioids, and the Calamites, all of which attained their maximum in the Carboniferous. Of these, the Lepidodendra may be regarded as gigantic, tree-like Club-mosses (Lycopodiacee) ; the Calamites are equally gigantic Horse-tails (Lquisetacee); and the Sigillarioids, equally huge in size, in some respects hold a position intermediate between the Club- mosses and the Pines (Conifers). ‘The Devonian rocks have DEVONTAN AND, OLD RED? PERIOD. ey) GENERALISED SECTION OF THE DEVONIAN ROCKS OF NortH AMERICA. Fig. 76. Z, = es m ,° . s Pin aes es oe Ses fy Seas eee Catskill Group. (oe) : ne ie < = ang fy te =e = Stic hate ta ke, ee e « --} ~ as = a » e . fan SSE Se e SSS = _————————————————— et rel Chemung Group. oa _—— =) SSIS eS Se OM ae a ee ee SA Se Se ea ea CE UN | Ree et eee Portage Group. x - = te o = © & i ear = Z, = a Hamilton Group. = x A co = a J S| Corniferous Limestone. = = De iol) GS 10)).6/( 0.8 jo.6\---— Schoharie Grit. BS -: Serre = 7, ae ae Spe ee inte | Ee : Wee Z g acer eirte otae e Cauda-Galli Grit. = A Oriskany Sandstone. Lower Helderberg. also yielded traces of many other plants (such as Annwlaria, A sterophyllites, Cardiocarpon, &c.), which acquire a greater pre- dominance in the Carboniferous period, and which will be spoken of in discussing the structure of the plants of the Coal- measures. Upon the whole, the one plant which may be con- sidered as specially characteristic of the Devonian (though not confined to this series) is the Pszophyton (fig. 77) of Dr Daw- son. These singular plants have slender branching stems, with sparse needle-shaped leaves, the young stems being at first coiled up, crosier-fashion, like the young fronds of ferns, whilst the old branches carry numerous spore-cases. The 138 HISTORICAL PALAZSONTOLOGY. stems and branches seem to have attained a height of two or three feet; and they sprang from prostrate “root-stocks” or Fig. 77.—Restoration of Pszio- phyton princeps. Devonian, Can- ada. (After Dawson.) creeping stems. Upon the whole, Principal Dawson is disposed to regard Pszlophyton as a ‘ general- ised type” of plants intermediate between the Ferns and the Club- mosses. Lastly, the Devonian de- posits have yielded the remains of the first actual ¢vees with which we “are as yet acquainted. About the nature of some of these (Ormoxylon and Dadoxylon) no doubt can be entertained, since their trunks not only show the concentric rings of growth characteristic of exogen- ous trees in general, but their woody tissue exhibits under the microscope the ‘‘ discs” which are characteristic of the wood of the Pines and Firs (see fig. 2). The singular genus /vofotaxites, how- ever, which occurs in an older por- tion of the Devonian series than * the above, is not in an absolutely unchallenged position. By Prin- cipal Dawson it is regarded as the trunk of an ancient Comzfer—the most ancient known; but Mr Carruthers regards it as more pro- bably the stem of a gigantic sea- weed. The trunks of Prototaxites (fig. 78, A) vary from one to three feet in diameter, and exhibit con- centric rings of growth; but its woody fibres have not hitherto been clearly demonstrated to pos- sess discs. Before leaving the Devonian vegetation, it may be mentioned that the hornstone or chert so abundant in the Corniferous limestone of North America has been shown to contain the remains of various microscopic plants (Diatoms and Desmids). We find also in the same siliceous material the singular spherical bodies, with radiating spines, which occur so abundantly in the chalk flints. and which are termed Xanthidia. These may be regarded DEVONIAN AND OLD RED PERIOD. 139 as probably the spore-cases of the minute plants known as Desmidie. A Pas X (i —~s2 fr —, a i ~ Ses \ = ys Fig. 78.—A, Trunk of Prototaxites Loganz, eighteen inches in diameter, as seen in the cliff near L’Anse Brehaut, Gaspé; B, Two wood-cells showing spiral fibres and obscure pores, highly magnified. Lower Devonian, Canada. (After Dawson.) The Devonian Profozoans have still to be fully investigat- ed. True Sponges (such as Astreospongia, Spherospongia, &c.) are not unknown; but by far the commonest repre- sentatives of this sub-kingdom in the Devonian strata are Stromatopora and its allies. These singular organisms (fig. 79) are not only very abundant in some of the Devonian lime- stones—both in the Old World and the New—but they often attain very large dimensions. However much they may differ in minor details, the general structure of these bodies is that of numerous, concentrically-arranged, thin, calcareous lamine, separated by narrow interspaces, which in turn are crossed by numerous delicate vertical pillars, giving the whole mass a cellular structure, and dividing it into innumerable minute quadrangular compartments. Many of the Devonian Stvomato- pore also exhibit on their surface the rounded openings of canals, which can hardly have served any other purpose than that of permitting the sea-water to gain ready access to every part of the organism. No true Graptolites have ever been detected in strata of 140 HISTORICAL PALZAONTOLOGY. Devonian age; and the whole of this group has become ex- tinguished—unless we refer here the still surviving Deictyoneme. 4 Z, i Fig. 79.—a, Part of the under surface of Stromatopora tuberculata, showing the wrinkled basement membrane and the openings of water-canals, of the natural size; 4, Portion of the upper surface of the same, enlarged ; c, Vertical section ofa fragment, mag- nified to show the internal structure. Corniferous Limestone, Canada. (Original.) The Celenterates, however, are represented by a vast number of Corals, of beautiful forms and very varied types. The marbles of Devonshire, the Devonian limestones of the Eifel and of France, and the calcareous strata of the Corniferous and Hamilton groups of America, are often replete with the skeletons of these organisms—so much so as to sometimes entitle the rock to be considered as representing an ancient coral-reef. In some instances the Corals have preserved their primitive calcareous composition ; and if they are embedded in soft shales, they may weather out of the rock in almost all their original perfection. In other cases, as in the marbles of Devonshire, the matrix is so compact and crystalline that the included corals can only be satisfactorily studied by means of polished sections. In other cases, again, the corals have been more or less completely converted into flint, as in the Cornifer- ous limestone of North America. When this is the case, they often come, by the action of the weather, to stand out from DEVONIAN AND OLD RED PERIOD. I4!I the enclosing rock in the boldest relief, exhibiting to the ob- server the most minute details of their organisation. As before, Fig. 81.—Zaphrentis cornicula, of the natural size. Devonian, America. (Ori- ginal.) Fig. 80.— Cystiphyllum vesiculosum, showing a succession of cups produced by budding from the original coral. Of the Fig. 82.—Heliophyllum exiguum, view- natural size. Devonian, America and ed from in front and behind. Of the natu- Europe. (Original.) ral size. Devonian, Canada. (Original.) the principal representatives of the Corals are still referable to the groups of the Rugosa and Zabulata. Amongst the Rugose group we find a vast number of simple “‘ cup-corals,” generally known by the quarrymen as “horns,” from their shape. Of 142 HISTORICAL’ PALZONTOLOGY. the many forms of these, the species of Cyathophyllum, Helio- phyllum (fig. 82), Zaphrentis (fig. 81), and Cystiphyllum (fig. 80), are perhaps those most abundantly represented—none of these genera, however, except He/iophyllum, being peculiar to the Devonian period. There are also numerous compound Ru- gose corals, such as species of Lridophyllum, Diphyphyl- lum, Syringopora, Phillipsastrea, and some of the forms of Cyathophyllum and Crepidophyllum (fig. 83). Some of these compound corals attain a very large size, and form of them- ‘s SSH » Fig. 83.—Portion of a mass of Crepidophyllum Archiact, of the natural size. Hamilton Formation, Canada. (After Billings.) selves regular beds, which have an analogy, at any rate, with existing coral-reefs, though there are grounds for believing that these ancient types differed from the modern reef-builders in being inhabitants of deep water. ‘The ‘“‘’Tabulate Corals” are hardly less abundant in the Devonian rocks than the Augosa ; and being invariably compound, they hardly yield to the latter in the dimensions of the aggregations which they sometimes form. The commonest, and at the same time the largest, of these are the ‘“‘honeycomb corals,” forming the genus /avosites (figs. 84, 85), which derive both their vernacular and their technical names from their great likeness to masses of petrified honeycomb. ‘The most abundant species are /avosites Goth- landica and F. hemispherica, both here figured, which form masses sometimes not less than two or three feet in diameter. Whilst avosctes has acquired a popular name by its honey- combed appearance, the resemblance of AZichelinia to a fossil- DEVONIAN AND OLD RED PERIOD. 143 ised wasp’s nest with the comb exposed is hardly less strik- ing, and has earned for it a similar recognition from the 38 once Oty ace 296%. 2 ane. rT} 8, CSA EES RS LS eee, Fig. 84.—Portion of amass of Favo- Fig. 85.—Fragment of Favosites hemi- sites Gothlandica, of the natural size. spherica, of the natural size. Upper Silu- Upper Silurian and Devonian of Europe rian-and Devonian of America. (After and America. (Original.) Billings.) non-scientific public. In addition to these, there are numer- ous branching or plant-like Tabulate Corals, often of the most graceful form, which are distinctive of the Devonian in all parts of the world. The LZchinoderms of the Devonian period call for little special notice. Many of the Devonian limestones are ‘crin- oidal ;” and the Crzmozds are the most abundant and widely- distributed representatives of their class in the deposits of this period. The Cystideans, with doubtful exceptions, have not been recognised in the Devonian ; and their place is taken by the allied group of the ‘‘ Pentremites,” which will be further spoken of as occurring in the Carboniferous rocks. On the other hand, the Star-fishes, Brittle-stars, and Sea-urchins are all continued by types more or less closely allied to those of the preceding Upper Silurian. Of the remains of Ringed-worms (Azwelides), the most numer- ous and the most interesting are the calcareous envelopes of some small tube-inhabiting species. No one who has visited the seaside can have failed to notice the little spiral tubes of the existing Sfzrorbzs growing attached to shells, or covering the fronds of the commoner Sea-weeds (especially Fucus ser- ratus). ‘These tubes are inhabited by a small Annelide, and structures of a similar character occur not uncommonly from the Upper. Silurian upwards. In the Devonian rocks, Spir- orbis 1s an extremely common fossil, growing in hundreds attached to the outer surface of corals and shells, and appearing 144 HISTORICAL PALZONTOLOGY. in many specific forms (figs. 86 and 87); but almost all the known examples are of small size, and are liable to escape a @. ; &§ WY TNS Fig. 87.—a, Spivorbis omphalodes, natural size and enlarged, Devonian, Europe and America ; 6, Spirerbis Arkonensis, of the natural size and enlarged ; c, The same, with the tube twisted in the reverse direction. Devonian, America. (Ori- ginal.) _Fig. 88.—a 4, Spirorbis laxus, enlarged, Upper Silurian, America; c, Spivorbis spinulifera, of the natural size and enlarged, Devonian, Canada. (Af- ter Hall and the Author.) cursory examination. The Crustaceans of the Devonian are prin- cipally Zurypterids and Trilobites. Some of the former attain gigantic dimensions, and the quarrymen intheScotch Old Red give them the name of “ seraphim,” from their singular scale-like ornamenta- tion. The Z7zlobites, though still sufficiently abundant in some local- ities, have undergone a yet further diminution since the close of the Upper Silurian. In both America and Europe quite a number of gen- eric types have survived from the Silurian, but few or no new ones make their appearance during this period in either the Old Fig. 88.—Devonian Trilobites a, Phacops latifrons, Devonian of Britain, the Conti- nent of Europe, and South America; 6, Homalonotus armatus, Europe; c, Phacops (Trimerocephalus) levis, Europe; a, Head-shield of Phacops (Portlockia) granulatus, Europe. (After Salter and Burmeister.) World or the New. The sfecies, however, are distinct ; and the DEVONIAN AND OLD RED PERIOD. 145, principal forms. belong to the genera Phacops (fig. 88, a, c, 2), Flomalonotus (fig. 88, 6), Proetus, and Bronteus. The species figured above under the name of Phacops latifrons (fig. 88, a), has an almost world-wide distribution, being found in the Devonian of Britain, Belgium, France, Germany, Russia, Spain, and South America ; whilst its place is taken in North Ame- rica by the closely-allied Phacops rana. In addition to the Trilobites, the Devonian deposits have yielded the remains of a number of the minute Ostracoda, such as Fintomis (“ Cypri- dina”), Leperditia, &c., which sometimes occur in vast num- bers, as in the so-called ‘‘ Cyprvidina Slates” of the German Devonian. There are also a few forms of Phyllopods (Es- theria). Taken as a whole, the Crustacean fauna of the Devonian period presents many alliances with that of the Upper Silurian, but has only slight relationships with that of the Lower Carboniferous. Besides Crustaceans, we meet here for the first time with the remains of az7-breathing Articulates, in the shape of Jusects. So far, these have only been obtained from the Devonian rocks of North America, and they indicate the existence of at least four generic types, all more or less allied to the existing May-flies (Ephemeride). One of these interesting primitive insects, namely, Platephemera antiqua (fig. 89), appears to have measured five inches in ex- panse of wing ; and another (Xenoneura antiquorum) has attached to its wing the re- mains of a “stridulating- organ ” similar to that pos- sessed by the modern Grass- hoppers—the instrument, as Principal Dawson remarks, of “the first music of living : é 2 Fig. 89.—Wing of Platephemera antigua. things that Geology as yet Devonian, America. (After Dawson.) reveals to us.” Amongst the Afollusca, the Devonian rocks have yielded a great number of the remains of Sea-mosses (Po/yzoa). Some of these belong to the ancient type Pre/odictya, which seems to disappear here, or to the allied Clathropora (fig. 90), with its fenestrated and reticulated fronds. We meet also with the graceful and delicate stems of Cerzofora (fig. 91). The majority of the Devonian /olyzoa belong, however, to the great and important Palzozoic group of the Lace-corals (Fenestella, figs. 92 and 94, Letepora, fig. 93, Polypora, and their allies). In all these forms there is a horny skeleton, of a K 140 HISTORICAL PALAEONTOLOGY. fan-like or funnel-shaped form, which grew attached by its base to some foreign body. ‘The frond consists of slightly- Fig. or. — Fragment of Ceriopora Hamiltonensis, of the natural size and enlarg- Fig. 90.—Fragment of Clathropora intertexta, of the ed. Devonian, Canada. (On- natural size and enlarged. Devonian, Canada. (Original.) ginal.) diverging or nearly parallel branches, which are either united by delicate cross-bars, or which bend alternately from side to side, and become directly united with one another at short intervals—in either case giving origin to numerous oval or ginal.) Fig. 92.—Fragment of Fenestella magnifica, Fig. 94.—Fragment of Fenestella of the natural size and enlarged. Devonian, cvébrosa, of the natural size and enlarg- Canada. (Original.) ed. Devonian, Canada. (Original.) oblong perforations, which communicate to the whole plant- like colony a characteristic netted and lace-like appearance. On one of its surfaces—sometimes the internal, sometimes the external—the frond carries a number of minute chambers or DEVONIAN AND OLD! RED’ PERIOD: 147 “cells,” which are generally borne in rows on the branches, and of which each originally contained a minute animal. The rachiopods still continue to be represented in great force through all the Devonian deposits, though not occurring in the true Old Red Sandstone. Besides such old types as Orthis, Strophomena, Lingula, Athyris, and Rhynchonella, we find some entirely new ones; whilst various types which only commenced their existence in the Upper Silurian, now under- go a great expansion and development. This last is especially the case with the two families of the Sfzrzfertd@ and the Pro- ductide. The Sfirifers, in particular, are especially character- istic of the Devonian, both in the Old and New Worlds —some of the most typical forms, such as Spirifera mucronata (fig. 96), having the shell “ winged,” or with the lateral angles prolonged S p ry, Rue ioe) B. 1. Calcaire Grossier. 1. Bagshot and Bracklesham beds. B. 2. Soissonnais Sands, or Lits 2. Wanting. Coquilliers. LOWER EOCENE. C. 1. Argile de Londres at base of I. London clay. Hill of Cassel, near Dun- kirk. C. 2. Argile plastique and lignite. 2. Plastic clay and sand with lig- nite (Woolwich and Reading series). C. 3. Sables de Bracheux. 3. Thanet sands. III. Eocene STRATA OF THE UNITED StatEes.—The low- est member of the Eocene deposits of North America is the so-called “ Lignitic Formation,” which is largely developed in Mississippi, Tennessee, Arkansas, Wyoming, Utah, Colorado, and California, and sometimes attains a thickness of several thousand feet. Stratigraphically, this formation exhibits the interesting point that it graduates downwards insensibly and conformably into the Cretaceous, whilst it is succeeded wncon- formably by strata of Middle Eocene age. Lithologically, the series consists principally of sands and clays, with beds of lig- nite and coal, and its organic remains show that it is principally of fresh-water origin with a partial intermixture of marine beds, THE EOCENE PERIOD. 289 _ These marine strata of the “ Lignitic formation ” are of special interest, as showing such a commingling of Cretaceous and Tertiary types of life, that it is impossible to draw any rigid line in this region between the Mesozoic and Kainozoic sys- tems. Thus the marine beds of the Lignitic series contain such characteristic Cretaceous forms as /zoceramus and Am- monites, along with a great number of Univalves of a distinctly Tertiary type (Cones, Cowries, &c.) Upon the whole, there- fore, we must regard this series of deposits as affording a kind of transition between the Cretaceous and the Eocene, holding in some respects a position which may be compared with that held by the Purbeck beds in Britain as regards the Jurassic and Cretaceous. The Middle Eocene of the United States is represented by the Clazborne and Jackson beds. The Clazborne series is extensively developed at Claiborne, Alabama, and consists of sands, clays, lignites, marls, and impure limestones, containing marine fossils along with numerous plant-remains. The /ack- son sertes is represented by lignitic clays and marls which occur at Jackson, Mississippi. Amongst the more remarkable fossils of this series are the teeth and bones of Cetaceans of the genus Zeuglodon. Strata of Upper Eocene age occur in North America at Vicksburg, Mississippi, and are known as the Vicksburg series. They consist of lignites, clays, marls, and limestones. Fresh- water deposits of Eocene age are also largely developed in parts of the Rocky Mountain region. The most remarkable fossils of these beds are Mammals, of which a large number of species have been already determined. LIFE OF THE EOCENE PERIOD. The fossils of the Eocene deposits are so numerous that nothing more can be attempted here than to give a brief and general sketch of the life of the period, special attention being directed to some of the more prominent and interesting types, amongst which—as throughout the Tertiary series—the Mam- mals hold the first place. It is not uncommon, indeed, to speak of the Tertiary period as a whole under the name of the ““ Age of Mammals,” a title at least as well deserved as that of “* Age of Reptiles” applied to the Mesozoic, or ‘‘ Age of Mol- luscs” applied to the Palzeozoic epoch. As regards the A/ants of the Eocene, the chief point to be noticed is, that the conditions which had already set in with the commencement of the Upper Cretaceous, are here con- T 290 HISTORICAL PALAZAONTOLOGY. tinued, and still further enforced. The Cycads of the Secondary period, if they have not totally disappeared, are exceedingly rare; and the Conifers, losing the predominance which they enjoyed in the Mesozoic, are now relegated to a subordinate though well-defined place in the terrestrial vegetation. ‘The great majority of the Eocene plants are referable to the groups of the Angiospermous Exogens and the Monocotyledons ; and the vegetation of the period, upon the whole, approximates closely to that now existing upon the earth. ‘The plants of the European Eocene are, however, in the main most closely allied to forms which are now characteristic of tropical or sub-tropical regions. ‘Thus, in the London Clay are found numerous fruits of Palms (Vifadites, fig. 213), along with various other plants, most of which indicate a warm climate as prevailing in the south of England at the commencement of the Eocene period. In the Eocene strata of North America occur numerous plants belong- ing to existing types—such as Palms, Conifers, the Magnolia, Cinnamon, Fig, Dog-wood, Maple,. Hickory, Poplar, Plane, &c. -Taken as ay wholewieee Eocene flora of North America is nearly related to that of the Miocene strata of Europe, as well as to that now existing p Big 21a Nitadites 22- «in: the American area. ) We mayeega London Clay, Isle es clude, therefore, that “the forests of the American Eocene resembled those of the European Miocene, and even of modern America” (Dana). As regards the auzmals of the Eocene period, the Protosoans are represented by numerous /oramzinifera, which reach here their maximum of development, both as regards the size of individuals and the number of generic types. Many of the Eocene Foraminifers are of small size; but even these not uncommonly form whole rock-masses. ‘Thus, the so-called “Miliolte Limestone” of the Paris basin, largely used as a building-stone, is almost wholly composed of the shells of a small species of Miliola. ‘The most remarkable, however, of the many members of this group of animals which flourished in Eocene times, are the “ Nummulites ” (Vwmmulina), so called from their resemblance in shape to coins (Lat. zawmmus, a coin). The Nummulites are amongst the largest of all known /ora- minifera, sometimes attaining a size of three inches in circum- ference ; and their internal structure is very complex (fig. 214). THE EOCENE PERIOD: 29I Many species are known, and they are particularly character- istic of the Middle and Upper of these periods—their place Fig. 214.—Nwmmulina levigata. ‘ Middle Eocene. being sometimes taken by Ovdcfordes,a form very similar to the Nummulite in external appearance, but differing in its internal details. In the Middle Eocene, the remains of Nummulites are found in vast numbers in a very widely-spread and easily- recognised formation known as the “‘ Nummulitic Limestone” (fig. 10). According to Sir Charles Lyell, “the Nummulitic Limestone of the Swiss Alps rises to more than Io,o00o feet above the level of the sea, and attains here and in other moun- tain-chains a thickness of several thousand feet. It may be said to play a far more conspicuous part than any other Tertiary group in the solid framework of the earth’s crust, whether in Europe, Asia, or Africa. It occurs in Algeria and Morocco, and has been traced from Egypt, where it was largely quarried of old for the building of the Pyramids, into Asia Minor, and across Persia by Bagdad to the mouths of the Indus. It has been observed not only in Cutch, but in the mountain-ranges which separate Scinde from Persia, and which form the passes leading to Cabul; and it has been followed still further east- ward into India, as far as Eastern Bengal and the frontiers of China.” The shells of Nummulites have been found at an elevation of 16,500 feet above the level of the sea in Western Thibet ; and the distinguished and philosophical geologist just quoted, further remarks, that ‘‘when we have once arrived at the conviction that the Nummulitic formation occupies a mid- dle and upper place in the Eocene series, we are struck with the comparatively modern date to which some of the greatest revolutions in the physical geography of Europe, Asia, and Northern Africa must be referred. All the mountain-chains— such as the Alps, Pyrenees, Carpathians, and Himalayas—ainto the composition of whose central and loftiest parts the Num- mulitic strata enter bodily, could have had no existence till 292 HISTORICAL PALAEONTOLOGY. after the Middle Eocene period. During that period, the sea prevailed where these chains now rise; for Nummulites and their accompanying Testacea were unquestionably inhabitants of salt water.” The Cwlenterates of the Eocene are represented principally by Corals, mostly of types identical with or nearly allied to those now in existence. Perhaps the most characteristic group of these is that of the Zurbinolide, comprising a number of simple “ cup-corals,” which probably lived in moderately deep water. One of the forms belonging to this family is here figured (fig. 215). Besides true Corals, the Eocene deposits have yielded the remains of the “Sea- pens” (Pennatulide) and the branched skeletons of the “‘Sea-shrubs” ( Govgonide). The £chinoderms are represented prin- cipally by Sea-urchins, and demand nothing more than mention. Itis to be observed, however, that the great group of the Sea- lilies (Crinoids) is now verging on extinc- tion, and is but very feebly represented. Amongst the A7o//usca, the Polyzoans and LBrachiopods also require no special men- tion, beyond the fact that the latter are greatly reduced in numbers, and belong principally to the existing genera TZere- bratula and Rhynchonella. ‘The Bivalves (Lamellibranchs) and the Univalves (Gas- teropods) are exceedingly numerous, and almost all the principal existing genera are now represented ; though less than five per cent of the Eocene sfecies are identical with those now living. It is difficult to make any selection from the many Bivalves which are known in deposits of this age ; but species of Cardita, Crassatella, Leda, Cyrena, Mactra, Cardium, Psammobia,&c., Fig. 215.—Turbinolia may be mentioned as very characteristic. Sia) Janta oe The Cardita planicosta here figured (fig. Eocene. 216) is not only very abundant in the Middle Eocene, but is very widely distri- buted, ranging from Europe to the Pacific coast of North America. The Uvivalves of the Eocene are extremely nu- merous, and generally beautifully preserved. The majority of them belong to that great section of the Gasterofods in which the mouth of the shell is notched or produced into THE EOCENE PERIOD. 293 a canal (when the shell is said to be ‘ siphonostomatous ”)— this section including the carnivorous and most highly-or- Fig. 216.—Cardita planicosta. Middle Eocene. ganised groups of the class. Not only is this the case, but a large number of the Eocene Univalves belong to types which now attain their maximum of development in the warmer regions of the globe. Thus we find numerous species of Cones (Conus), Volutes ( Voluta), Cowries (Cyprea, fig. 218), Fig. 217.—Typhis tubifer, a ‘‘siphonosto- Fig. 218. — Cyfrea matous ” Univalve. Eocene. elegans. Eocene. Olives and Rice-shells (OZva), Mitre-shells (J/tra), Trumpet- shells (Z7zfon), Auger-shells (Zerebra), and Fig-shells (Pyru/a). Along with these are many forms of Pleurotoma, Rostellaria, Spindle-shells (Fusws), Dog-whelks (Vassa), Murices, and many round-mouthed (“ holostomatous ”) species, belonging to such genera as Turritella, Nerita, Natica, Scalaria, &c. The genus Cerithium (fig. 219), most of the living forms of which are found in warm regions, inhabiting fresh or brackish waters, undergoes a vast development in the Eocene period, where it 204 HISTORICAL PALEONTOLOGY. is represented by an immense number of specific forms, some of which attain very large dimensions. In the Eocene strata of the Paris basin alone, nearly one hundred and fifty species of this genus have been detected. The more strictly fresh - water deposits of the Eocene period have also yielded numerous remains of Univalves such as are now proper to rivers and lakes, to- gether with the shells of true Land-snails. Amongst these may be mentioned numerous species of Limnea (fig. 220), Physa (fig. 221), Melania, Paludina, Planorbis, Helix, Buli- mus, and Cyclostoma ‘fig. 222). With regard to the Cephalopods, the chief point to be noticed is, that all the beautiful : and complex forms which peculiarly char- Fig. 219.—Cerithi- acterised the Cretaceous period have here we eee Fo disappeared. We no longer meet with a single example of the Turrilite, the Baculite, the Hamite, the Scaphite, or the Ammonite. The only ex- ception to this statement is the occurrence of one species Fig. 220.—Limnea Fig. 221.—Physa Fig. 222.—Cyclostoma pyramidalis. Eocene. coluninaris. Eocene. Arnoudit. Eocene. of Ammonite in the so-called “ Lignitic Formation” of North America ; but the beds containing this may possibly be rather referable to the Cretaceous—and this exception does not affect the fact that the Ammonitide, as a family, had be- come extinct before the Eocene strata were deposited. The | ancient genus /Vaz/z/us still survives, the sole representative of the once mighty order of the Tetrabranchiate Cephalopods. In the order of the Dzbranchiates, we have a like phenomenon to observe in the total extinction of the great family of the “‘ Belemnites.” No form referable to this group has hitherto THE EOCENE PERIOD. 295 been found in any Tertiary stratum; but the internal skeletons of Cuttle-fishes (such as 4elosepia) are not unknown. Remains of /zshes are very abundant in strata of Eocene age, especially in certain localities. The most famous depot for the fossil fishes of this period is the hmestone of Monte Bolca, near Verona, which is interstratified with beds of vol- caric ashes, the whole being referable to the Middle Eocene. The fishes here seem to have been suddenly destroyed by a volcanic eruption, and are found in vast numbers. Agassiz has described over one hundred and thirty species of Fishes from this locality, belonging to seventy-seven genera. All the species are extinct; but about one-half of the gevera are represented by living forms. The great majority of the Fig. 223.—Rhombus minimus, a small fossil Turbot from the Eocene Tertiary, Monte Bolca. Eocene Fishes belong to the order of the “ Bony Fishes” ( Zeleosteans), so that in the main the forms of. Fishes charac- terising the Eocene are similar to those which predominate in existing seas. In addition to the above, a few Gavoids and a large number of P/acoids are known to occur in the Eocene rocks. Amongst the latter are found numerous teeth of true Sharks, such as Ofodus (fig. 224) and Carcharodon. The pointed and serrated teeth of the latter sometimes attain a length of over half a foot, indicating that these predaceous fishes attained gigantic dimensions; and it is interesting to note that teeth, in external appearance very similar to those of the early Tertiary genus Carcharodon, have been dredged from great depths during the recent expedition of the Chal- lenger. There also occur not uncommonly the flattened 296 HISTORICAL PALAEONTOLOGY. teeth of Rays (fig. 225), consisting of flat bony pieces placed close together, and forming “a kind of mosaic pavement on both the upper and lower jaws” (Owen). In the class of the /eptiles, the disappearance of the char- "SESS SS: Lay In KA i Fig. 224.—Tooth of Fig. 225.—Flattened dental plates of a Ray Opes obliguus. (Myliobatis Edwardsii). Eocene. ocene. acteristic Mesozoic types is as marked a phenomenon as the introduction of new forms. The Ichthyosaurs, the Plesio- saurs, the Pterosaurs, and the Mosasaurs of the Mesozoic, find no representatives in the Eocene Tertiary ; and the same is true of the Deinosaurs, if we except a few remains from the doubtfully-situated “ Lignitic formation ” of the United States. On the other hand, all the modern orders of Reptiles are known to have existed during the Eocene period. The Chelonians are represented by true marine Turtles, by “ Ter- rapins” (Hmydide), and by “Soft Tortoises” ( Trionycide). The order of the Snakes and Serpents (Of/idia) makes its appearance here for the first time under several forms—all of ae however, are referable to the non-venomous group of the = Constricting Serpents” (ode). The oldest of these iS ce Paleophis “toliapicus of the London Clay of Sheppey, first made known to science by the researches ot Professor Owen. The nearly-allied Paleophis typheus of the Eocene beds of Bracklesham appears to have been a Boa-constrictor- like Snake of about twenty feet in length. Similar Python- like Snakes (Paleophis, Dinophis, &c.) have been described from the Eocene deposits of the United States. True Lizards (Lacertilians) are found in some abundance in the Eocene deposits,—some being small terrestrial forms, like the common European lizards of the present day ; whilst,others equal or exceed the living Monitors in size. Lastly, the modern order of the Crocodilia is largely represented in Eocene times, by - species belonging to all the existing genera, together with others referable to extinct types. As pointed out by Owen, it is an interesting fact that in the Eocene rocks of the south- THE EOCENE PERIOD. 297 west of England, there occur fossil remains of all the three living types of Crocodilians—namely, the Gavials, the true Crocodiles, and the Alligators (fig. 226)—though at the Fig. 226.—Upper jaw of Alligator. Eocene Tertiary, Isle of Wight. present day these forms are all geographically restricted in their range, and are never associated together. Almost all the existing orders of Azrds, if not all, are represented in the Eocene deposits by remains often very closely allied to existing types. Thus, amongst the Swimming Birds ((Vatatores) we find examples of forms allied to the living Pelicans and Mergansers; amongst the Waders (Gra/- Jatores) we have birds resembling the Ibis (the Mumenzius gypsorum of the Paris basin); amongst the Running Birds (Cursores) we meet with the great Gastornis Parisiensis, which equalled the African Ostrich in height, and the still more gigantic Dasornis Londinensts; remains of a Partridge rep- resent the Scratching Birds (Rasores) ; the American Eocene has yielded the bones of one of the Climbing Birds (.Scan- sores), apparently referable to the Woodpeckers ; the Profornis Glarisiensis of the Eocene Schists of Glaris is the oldest known example of the Perching Birds (/msessores); and the Birds of Prey (Raptores) are represented by Vultures, Owls, and Hawks. The toothed Birds of the Upper Cretaceous are no longer known to exist; but Professor Owen has recently described from the London Clay the skull of a very remarkable Bird, in which there is, at any rate, an approxi- mation to the structure of /chthyornis and Fesperornis. The bird in question has been named the Odontopteryx toliapicus, its generic title being derived from the very remarkable char- acters of its jaws. In this singular form (fig. 227) the margins 298 HISTORICAL PALZONTOLOGY. of both jaws are iurnished with tooth-like denticulations, which differ from true teeth in being actually portions of the bony — ee / PRO en BES Fig. 227.—Skull of Odontopteryx toliapicus, restored. (After Owen.) substance of the jaw itself, with which they are continuous, and which were probably encased by extensions of the horny sheath of the bill. These tooth-like processes are of two sizes, the larger ones being comparable to canines ; and they are all directed forwards, and have a triangular or compressed conical form. From a careful consideration of all the dis- covered remains of this bird, Professor Owen concludes that “* Odontopteryx was a warm-blooded feathered biped, with wings; and further, that it was web-footed and a fish-eater, and that in the catching of its slippery prey it was assisted by this Pterosauroid armature of its jaws.” Upon the whole, Odontopteryx would appear to be most nearly related to the family of the Geese (Azserine) or Ducks (Anatide); but the extension of the bony substance of the jaws into tooth-like processes is an entirely unique character, in which it stands quite alone. The known JZammatls of the Mesozoic period, as we have seen, are all of small size; and with one not unequivocal exception, they appear to be referable to the order of the Pouched Quadrupeds (JZarsufials), almost the lowest group of the whole class of the Wammata. In the Eocene rocks, on the other hand, numerous remains of Quadrupeds have been brought to light, representing most of the great Mam- malian orders now in existence upon the earth, and in many cases indicating animals of very considerable dimensions. We are, in fact, in a position to assert that the majority of the great groups of Quadrupeds with which we are familiar at the present day were already in existence in the Eocene period, and that their ancient root-stocks were even in this early time separated by most of the fundamental differences of structure THE EOCENE PERIOD. 299 which distinguish their living representatives. At the same time, there are some amongst the Eocene quadrupeds which have a “ generalised” character, and which may be regarded as structural types standing midway between groups now sharply separated from one another. The order of the JZarsupia/s—including the existing Kan- garoos, Wombats, Opossums, Phalangers, &c.— is poorly represented in deposits of Eocene age. ‘The most celebrated example of this group is the Dvzdelphys gypsorum of the Gypseous beds of Montmartre, near Paris, an Opossum very nearly allied to the living Opossums of North and South America. No member of the Ldentates (Sloths, Ant-eaters, and Arma- dillos) has hitherto been detected in any Eocene deposit. The aquatic order of the Szvenians (Dugongs and Manatees), with their fish-like bodies and tails, paddle- shaped fore- limbs, and wholly deficient hind-limbs, are represented in strata of this age by remains of the ancient ‘“ Sea-Cows,” to which the name of Hadlitherium has been applied. Nearly allied to the preceding is the likewise aquatic order of the Whales and Dolphins (Céefaceans), in which the body is also fish-like, the hind-limbs are wanting, the fore-limbs are con- verted into powerful “flippers” or swimming-paddles, and the terminal extremity of the body is furnished with a horizontal tail-fin. Many existing Cetaceans (such as the Whalebone Whales) have no true teeth; but others (Dol- phins, Porpoises, Sperm Whales) possess simple conical teeth. Fig. 228.—Zeuglodon cetoides. A, Molar tooth of the natural size; B, Vertebra, reduced in size. From the Middle Eocene of the United States. (After Lyell.) In strata of Eocene age, however, we find a singular group of Whales, constituting the genus Zeuglodon (fig. 228), in 300 HISTORICAL PALASONTOLOGY. which the teeth differed from those of all existing forms in being of two kinds,—the front ones being conical incisors, whilst the back teeth or molars have serrated triangular crowns, and are inserted in the jaw by two roots. Each molar (fig. 228, A) looks as if it were composed of two separate teeth united on one side by their crowns; and it is this peculiarity which is expressed by the generic name (Gr. zeugle, a yoke ; odous, tooth). The best-known species of the genus is the Zeuglodon cetoides of Owen, which attained a length of seventy feet, Remains of these gigantic Whales are very common in the “Jackson Beds” of the Southern United States. So common are they that, according to Dana, ‘the large vertebree, some of them a foot and a half long and a foot in diameter, were formerly so abundant over the country, in Alabama, that they were used for making walls, or were burned to rid the fields of them.” The great and important order of the Hoofed Quadrupeds ( Ungulata) is represented in the Eocene by examples of both ot its two principal sections—namely, those with an uneven number of toes (one or three) on the foot (Perissodactyle Ungu- éates), and those with an even number of toes (two or four) to each foot (Artiodactyle Ungulates). Amongst the Odd-toed Ungulates, the living family of the Tapirs (Ti apiridé) 1s repre- sented by the genus Coryphodon of Owen. Nearly related to the preceding are the species of Padeotherium, which have a historical interest as being amongst the first of the Tertiary Mammals investigated by the illustrious Cuvier. Several species of Paleothere are known, varying greatly in size, the smallest being little bigger than a ‘hare, whilst the largest must have equalled a good-sized horse in its dimensions. The species of Paleotherium appear to have agreed with the existing Tapirs in possessing a lengthened and flexible nose, which formed a short proboscis or trunk (fig. 229), suitable as an instrument for stripping off the foliage of trees—the char- acters of the molar teeth showing them ‘to have been strictly herbivorous in their habits. They differ, however, from the Tapirs, amongst other characters, in the fact that both the fore and the hind feet possessed three toes each ; whereas in the latter there are four toes on each fore-foot, and the hind- feet alone are three-toed. The remains of Paleotheria have been found in such abundance in certain localities as to show that these animals roamed in great herds over the fertile plains of France and the south of England during the later portion of the Eocene period. The accompanying illustration (fig. 229) represents the notion which the great Cuvier was induced THE EOCENE: PERIOD. 301 by his researches to form as to the outward appearance of Paleotherium magnum. Recent discoveries, however, have = = Fae My We as & ae With <= ea - : = fee ———— ae = ZEW" «gni7 i ES ax) —— Fig .229 —Outline of Padeotherium magnum, restored. Upper Eocene, Europe. fter Cuvier.) rendered it probable that this restoration is in some important respects inaccurate. Instead of being bulky, massive, and more or less resembling the living Tapirs in form, it would rather appear that Paleotherium magnum was in reality a slender, graceful, and long-necked animal, more closely resembling in general figure a Llama, or certain of the Antelopes. The singular genus Anchithertum forms a kind of transition between the Pa/gotheria and the true Horses (Zguide). The Horse (fig. 230, D) possesses but one fully-developed toe to each foot, this being terminated by a single broad hoof, and representing the mzddle toe—the ¢hird of the typical five- fingered or five-toed limb of Quadrupeds in general. In addition, however, to this fully-developed toe, each foot in the horse carries two rudimentary toes which are concealed beneath the skin, and are known as the “splint-bones.” These are respectively the second and fourth toes, in an aborted condition; and the fst and f/th toes are wholly wanting. In Azpparion (fig. 230, C), the foot is essentially like that of the modern Horses, except that the second and fourth toes no longer are mere “splint-bones,” hidden be- neath the skin; but have now little hoofs, and hang freely, but uselessly, by the side of the creat middle toe, not being sufficiently developed to reach the ground. In Anchitherium, again (fig. 230, B), the foot is three-toed, like that of Azpparion, but the two lateral toes (the second and fourth) are so far 302 HISTORICAL PALAZONTOLOGY. developed that they now reach the ground. The jrs¢ digit (thumb or great toe) is still wanting ; as also is the 77/¢h digit Fig. 230.—Skeleton of the foot in various forms belonging to the family of the Eguzde. A, Foot of Orohippus, Eocene ; B, Foot of Anchitherium, Upper Eocene and Lower Miocene; C, Foot of Hipparion, Upper Miocene and Pliocene ; D, Foot of Horse (Zguus), Pliocene and Recent. The figures indicate the numbers of the digits in the typical five-fingered hand of Mammals. (After Marsh.) (little finger or little toe). Lastly, the Eocene rocks have yielded in North America the remains of a small Equine quadruped, to which Marsh has given the name of Ovohippus. In this singular form—which was not larger than a fox—the foot (fig. 230, A) carries four toes, all of which are hoofed and touch the ground, but of which the ¢/z7¢ toe is still the largest. The frst toe (thumb or great toe) is still wanting ; but in this ancient representative of the Horses, the 7/¢A or “little” toe appears for the first time. As all the above-mentioned forms succeed one another in point of time, it may be regarded as probable that we shall yet be able to point, with some cer- tainty, to some still older example of the guide, in which the first digit is developed, and the foot assumes its typical five-fingered condition: Passing on to the Even-toed or Avtiodactyle Ungulates, no representative of the AZzppotamus seems yet to have existed, but there are several forms (Cheropotamus, Hyopotamus, &c.) more or less closely allied to the Pigs (Swzda); and the singular group of the Avxoplotheride may be regarded as form- ing a kind of transition between the Swine and the Ruminants. The Anoplotheria (fig. 231) were slender in form, the largest not exceeding a donkey in size, with long tails, and having the feet terminated by two hoofed toes each, sometimes with a pair of small accessory hoofs as well. The teeth exhibit the THE EOCENE PERIOD. 303 peculiarity that they are arranged in a continuous series, with- out any gap or interval between the molars and the canines; and Fig. 231.—Anoplotherium commune. Eocene Tertiary, France. (After Cuvier.) the back teeth, like those of all the Ungulates, are adapted for grinding vegetable food, their crowns resembling in form those of the true Ruminants. The genera Dichobune and Xiphodon, of the Middle and Upper Eocene, are closely related to Anoplotherium, but are more slender and deer-like in form. No example of the great Ruminant group of the Ungulate Quadrupeds has as yet been detected in deposits of Eocene age. Whilst true Ruminants appear to be unknown, the Eocene strata of North America have yielded to the researches of Professor Marsh examples of an extraordinary group (L2zv0- cerata), which may be considered as in some respects inter- mediate between the Ungulates and the Proboscideans. In Dinoceras itself (fig. 232) we have a large animal, equal in dimensions to the living Elephants, which it further resembles in the structure of the massive limbs, except that there are only four toes to each foot. The upper jaw was devoid of front teeth, but there were two very large canine teeth, in the form of tusks directed perpendicularly downwards ; and there was also a series of six small molars on each. Each upper jaw-bone carried a bony projection, which was probably of the nature of a “‘horn-core,” and was originally sheathed in horn. Two similar, but smaller, horn-cores are carried on the nasal bones ; and two much larger projections, also probably of the nature of horn-cores, were carried upon the forehead. We may thus infer that Dzwoceras possessed three pairs of horns, all of which resembled the horns of the Sheep and Oxen in consisting of a central bony ‘‘core,” surrounded by a horny 304 HISTORICAL PALZVONTOLOGY. sheath. The nose was not prolonged into a proboscis or “trunk,” as in the existing Elephants ; and the tail was short Fig. 232.—Skull of Dizoceras mirabilis, greatly reduced. Eocene, North America. (After Marsh.) and slender. Many forms of the Dinocerata are known ; but all these singular and gigantic quadrupeds appear to have been confined to the North American continent, and to be restricted to the Eocene period. The important order of the Elephants (Prodoscidea) is also not known to have come into existence during the Eocene period. On the other hand, the great order of the Beasts of Prey (Carnivora) is represented in Eocene strata by several forms belonging to different types. ‘Thus the A7cfocyon pre- sents us with an Eocene Carnivore more or less closely allied to the existing Racoons; the Pa/gonyctis appears to be related to the recent Civet-cats; the genus Ayenodon is in some respects comparable to the living Hyzenas; and the Camzs Parisiensis of the gypsum-bearing beds of Montmartre may perhaps be allied to the Foxes. The order of the Bats (Chetroptera) is represented in Eocene strata of the Paris basin (Gypseous series of Montmartre) by the Vespertilid Parisiensis (fig. 233), an insect-eating Bat very similar to some of the existing European forms. Lastly, the Eocene deposits have yielded more or less satisfactory evi- THE MIOCENE PERIOD. 305 dence of the existence in Europe at this period of examples of the orders of the Gnawing Mammals (Aodentia), the Insect- Fig. 233.—Portion of the skeleton of Vesfertilio Parisiensis. Eocene Tertiary, France. eating Mammals (/msectivora), and the Monkeys (Quadru- mana).* CART Tike (2G Xe LITLE MIOCENE PERIOD: The Miocene rocks comprise those Tertiary deposits which contain less than about 35 per cent of existing species of shells (Mollusca), and more than 5 per cent—or those deposits in which the proportion of living shells is less than of extinct species. They are divisible into a Lower Miocene (Oligocene) and an Upper Miocene series. In Britain, the Miocene rocks are very poorly developed, one of their leading developments being at Bovey Tracy in Devonshire, where there occur sands, clays, and beds of lignite * A short list of the more important works relating to the Eocene rocks and fossils will be given after all the Tertiary deposits have been treated of. U 306 HISTORICAL .PALAZONTOLOGY. or imperfect coal. These strata contain numerous plants, amongst which are Vines, Figs, the Cinnamon-tree, Palms, and many Conifers, especially those belonging to the genus Sequoia (the ‘‘Red-woods’’). These Bovey Tracy lignites are of Lower Miocene age, and they are lacustrine in origin. Also of Lower Miocene age are the so-called ‘‘ Hempstead Beds ” of Yarmouth in the Isle of Wight. These attain a thickness of less than 200 feet, and are shown by their numerous fossils to be principally a true marine formation. Lastly, the Duke of Argyll, in 1851, showed that there existed at Ardtun, in the island of Mull, certain Tertiary strata containing numerous remains of plants ; and these also are now regarded as belong- ing to the Lower Miocene. In France, the Lower Miocene is represented in Auvergne, Cantal, and Velay, by a great thickness of nearly horizontal strata of sands, sandstone, clays, marls, and limestones, the whole of fresh-water origin. The principal fossils of these lacustrine deposits are AZammatlia, of which the remains occur in great abundance. In the valley of the Loire occur the typical European deposits of Upper Miocene age. ‘These are known as the “ Faluns,”’ from a provincial term applied to shelly sands, employed to spread upon soils which are deficient in lime; and the Upper Miocene is hence sometimes spoken of as the “ Falunian” formation. The Faluns occur in scat- tered patches, which are rarely more than 50 feet in thickness, and consist of sands and marls. The fossils are chiefly marine; but there occur also land and fresh-water shells, together wie the remains of numerous Mammals. About 25 per cent of the shells of the Faluns are identical with existing species. The sands, limestones, and marls of the Department of Gers, near the base of the Pyrenees, rendered famous by the number of Mammalian remains exhumed from them by M. Lartet, also belong to the age of the Faluns. In Switzerland, between the Alps and the Jura, there occurs a great series of Miocene deposits, known collectively as the “ Molasse,” from the soft nature of a greenish sandstone, which constitutes one of its chief members. It attains a thick- ness of many thousands of feet, and rises into lofty mountains, some of which—as the Rigi—are more than 6000 feet in height. The middle portion of the Molasse is of marine origin, and is shown by its fossils to be of the age of the Faluns; but the lower and upper portions of the formation are mainly or entirely of fresh-water origin. The Lower Molasse (of Lower Miocene age) has yielded about 500 species of plants, mostly of tropical or sub-tropical forms. ‘The Upper THE. MIOCENE PERIOD. 307 Molasse has yielded about the same number of plants, with about goo species of Insects, such as wood-eating Beetles Water-beetles, White Ants, Dragon-flies, &c. In Lelgtum, strata of both Lower and Upper Miocene age are known,—the former (2upelian Clays) containing numerous marine fossils; whilst the latter (Bolderberg Sands) have yielded numerous shells corresponding with those of the Faluns. In Austria, Miocene strata are largely developed, marine beds belonging to both the Lower and Upper division of the formation occurring extensively in the Vienna basin. The well-known Brown Coals of Radaboj, in Croatia, with numer- ous plants and insects, are also of Lower Miocene age. In Germany, deposits belonging to both the Lower and Upper division of the Miocene formation are extensively de- veloped. ‘To the former belong the marine strata of the May- ence basin, and the marine Aupelian Clay near Perlin ; whilst a celebrated group of strata belonging to the Upper Miocene occurs near Epplesheim, in Hesse-Darmstadt, and is well known for the number of its Mammalian remains. In Greece, at Pikermé, near Athens, there occurs a celebrated deposit of Upper Miocene age, well known to paleontologists through the researches of M.M. Wagner, Roth, and Gaudry upon the numerous Mammalia which it contains. In /fa/y, also, strata of both Lower and Upper Miocene age are well developed in the neighbourhood of Turin. In the Szwalik Hills, in India, at the southern foot of the Himalayas, occurs a series of Upper Miocene strata, which have become widely celebrated through the researches of Dr Falconer and Sir Proby Cautley upon the numerous remains of Mammals and Reptiles which they contain. Beds of corre- sponding age, with similar fossils, are known to occur in the island of Perim in the Gulf of Cambay. Lastly, Miocene deposits are found in Worth America, in New Jersey, Maryland, Virginia, Missouri, California, Oregon, &c., attaining a thickness of 1500 feet or more. They consist principally of clays, sands, and sandstones, sometimes of marine and sometimes of fresh-water origin. Near Richmond, in Virginia, there occurs a remarkable stratum, wrongly called “ Tnfusorial Earth,” which is occasionally 30 feet in thickness, and consists almost wholly of the siliceous envelopes of cer- tain low forms of plants (Diatoms), along with the spicules of Sponges and other siliceous organisms (see fig. 16). The White River Group of Hayden occurs in the Upper Missouri region, and is largely exposed over the barren and desolate 308 HISTORICAL PALAEONTOLOGY. district known as the “ Mauvaises Terres.” They have a thickness of 1000 feet or more, and contain numerous remains of Mammals. ‘They are of lacustrine origin, and are believed to be of the age of the Lower Miocene. Upon the whole, about from 15 to 30 per cent of the J/o//usca of the American Miocene are identical with existing species. In addition to the regions previously enumerated, Miocene strata are known to be developed in Greenland, Iceland, Spitz- bergen, and in other areas of less importance. The “fe of the Miocene period is extremely abundant, and, from the nature of the deposits of this age, also extremely varied in its character. The marine beds of the formation have yielded numerous remains of both Vertebrate and Inver- tebrate sea-animals; whilst the fresh-water deposits contain the skeletons of such shells, fishes, &c., as now inhabit rivers or lakes. Both the marine and the lacustrine beds have been shown to contain an enormous number of plants, the latter more particularly ; whilst the Brown Coals of the formation are made up of vegetable matter little altered from its original condition. The remains of air-breathing animals, such as Insects, Reptiles, Birds, and Mammals, are also abundantly found, more especially in the fresh-water beds. The plants of the Miocene period are extraordinarily num- erous, and only some of the general features of the vegetation of this epoch can be indicated here. Our chief sources of informa- tion as to the Miocene plants are the Brown Coals of Germany and Austria, the Lower and Upper Molasse of Switzerland, and the Miocene strata of the Arctic regions. The lignites of Austria have yielded very numerous plants, chiefly of a tropical character—one of the most noticeable forms being a Palm of the genus Sadal (fig. 234, B), now found in America. The plants of the Lower Miocene of Switzerland are also mostly of a tropical character, but include several forms now found in North America, such as a Tulip-tree (Ziriodendron) and a Cypress (Zaxodium). Amongst the more remarkable forms from these beds may be mentioned Fan-Palms (Chame@rops, fig. 234, A), numerous tropical ferns, and two species of Cin- namon. ‘The plant-remains of the Upper Molasse of Switzer- land indicate an extraordinarily rank and luxuriant vegetation, composed mainly of plants which now live in warm countries. Among the commoner plants of this formation may be enume- rated many species of Maple (Acer), Plane-trees (Platanus fig. 235), Cinnamon-trees (fig. 236), and other members of the Lauracee, many species of Proteacce (Banksia, Grevillea, &c.), several species of Sarsaparilla (Swz/ax), Palms, Cypresses, &c. THE MIOCENE PERIOD. 309 In Britain, the Lower Miocene strata of Bovey Tracy have yielded remains of Ferns, Vines, Fig, Cinnamon, Proteacee, \\ \ Ati Wy , Y SE \ ican Fig. 234.—Miocene Palms A, Chamerops Helvetica; B, Sabal major. Lower Miocene of Switzerland and France. &c., along with numerous Conifers. The most abundant of these last is a gigantic pine—the Seguota Couttste—which is Fig. 235-—Platanus aceroides, an Fig. 236. — Cinnamio- Upper Miocene Plane-tree. a, Leaf; mune polymorphun. a, 6, The core of a bundle of fruits; c, Leaf; 4, Flower. Upper A single fruit. Miocene. very nearly allied to the huge Seguoza (Wellingtonia) gigantea of California. A nearly-allied form (Seguota Langsdorffi) has been detected in the leaf-bed of Ardtun, in the Hebrides. In Greenland, as well as in other parts of the Arctic regions, Miocene strata have been discovered which have yielded a great number of plants, many of which are identical with species found in the European Miocene. Amongst these 310 HISTORICAL PALZONTOLOGY. plants are found many trees, such as Conifers, Beeches, Oaks, Maples, Plane-trees, Walnuts, Magnolias, &c., with numerous shrubs, ferns, and other smaller plants. With regard to the Miocene flora of the Arctic regions, Sir Charles Lyell remarks that ‘more than thirty species of Coniferee have been found, including several Sequoias (allied to the gigantic Wellingtonia of California), with species of Zhwjopsis and Salisburia, now peculiar to Japan. There are also beeches, oaks, planes, poplars, maples, walnuts, limes, and even a magnolia, two cones of which have recently been obtained, proving that this splendid evergreen not only lived but ripened its fruit within the Arctic circle. Many of the limes, planes, and oaks were large-leaved species; and both flowers and fruits, besides immense quantities of leaves, are in many cases pre- served. Among the shrubs are many evergreens, as Azdro- meda, and two extinct genera, Daphnogene and M1‘ Cliniockia, with fine leathery leaves, together with hazel, blackthorn, holly, logwood, and hawthorn. A species of Zamia (Zamiites) grew in the swamps, with Potamogeton, Sparganium, and Menyanthes; while ivy and vines twined around the forest- trees, and broad-leaved ferns grew beneath their shade. Even in Spitzbergen, as far north as lat. 78° 56’, no less than ninety- five species of fossil plants have been obtained, including Taxodium of two species, hazel, poplar, alder, beech, plane- tree, and lime. Such a vigorous growth of trees within 12° of the pole, where now a dwarf willow and a few herbaceous plants form the only vegetation, and where the ground is covered with almost perpetual snow and ice, is truly remark- able.” Taking the Miocene flora as a whole, Dr Heer concludes from his study of about 3000 plants contained in the Euro- pean Miocene alone, that the Miocene plants indicate tropical or sub-tropical conditions, but that there is a striking inter- mixture of forms which are at present found in countries widely removed from one another. It is impossible to state with certainty how many of the Miocene plants belong to existing species, but it appears that the larger number are extinct. According to Heer, the American types of plants are most largely represented in the Miocene flora, next those of Europe and Asia, next those of Africa, and lastly those of Australia. Upon the whole, however, the Miocene flora of Europe is mostly nearly allied to the plants which we now find inhabiting the warmer parts of the United States; and this has led to the suggestion that in Miocene times the Atlantic Ocean was dry land, and that a migration of Ameri- THE MIOCENE .PERIOD. Srl can plants to Europe was thus permitted. This view is borne out by the fact that the Miocene plants of Europe are most nearly allied to the living plants of the eastern or Atlantic seaboard of the United States, and also by the occurrence of a rich Miocene flora in Greenland. As regards Greenland, Dr Heer has determined that the Miocene plants indicate a temperate climate in that country, with a mean annual tem- perature at least 30° warmer than it is at present. The present limit of trees is the isothermal which gives the mean temperature of 50° Fahr. in July, or about the parallel of 67° N. latitude. In Miocene times, however, the Limes, Cypresses, and Plane-trees reach the 79th degree of latitude, and the Pines and Poplars must have ranged even further north than this. The Lnvertebrate Animals of the Miocene period are very numerous, but they belong for the most part to existing types, and they can only receive scanty consideration here. The little shells of Foraminifera are extremely abundant in some beds, the genera being in many cases such as now flourish abundantly in our seas. The principal forms belong to the genera TZextularia (fig. 237), Robulina, Glandulina, Poly- stomella, Amphistegina, &c. Corals are very abundant, in many instances forming regular “‘ reefs ;” but all the more important groups are in existence at the present day. The Red Coral (Cor- allium), so largely sought after as an ornamental ma- terial, appears for the first s time in deposits of this age. ** "ae Amongst the Zchinoderms, we meet with Heart-Urchins (Spatangus), Cake - Urchins (Scutella, fig. 238), and various other forms, the majority of which are ciosely allied to forms now in existence. Numerous Crabs and Lobsters represent the Crustacea; but the most important of the Miocene Articulate Animals are the Insects. Of these, more than thirteen hundred species have been determined by Dr Heer from the Miocene strata of Switzerland alone. They include almost all the existing orders of insects, such as numerous and varied forms of Beetles (Coleoptera), Forest-bugs (Hemiptera), Ants (Hymen- optera), Flies (Diptera), Termites and Dragon- flies (Weurop- tera), Grasshoppers (Orthoprera), and Butterflies (Lepidoptera). 312 HISTORICAL PALEONTOLOGY. One of the latter, the well-known Vanessa Pluto of the Brown Coals of Croatia, even exhibits the pattern of the wing, and to Fig. 238.—Different views of Scatella subrotunda, a Miocene “ Cake-Urchin” from the south of France. some extent its original coloration ; whilst the more durably- constructed insects are often in a state of exquisite preser- vation. The JAZollusca of the Miocene period are very numerous, but call for little special comment. Upon the whole, they are generically very similar to the Shell-fish of the present day ; whilst, as before stated, from fifteen to thirty per cent of the species are identical with those now in existence. So far as the European area is concerned, the Molluscs indicate a decidedly hotter climate than the present one, though they have not such a distinctly tropical character as is the case with the Eocene shells. Thus we meet with many Cones, Volutes, Cowries, Olive-shells, Fig-shells, and the like, which are decidedly indicative of a high temperature of the sea. olyzoans are abundant, and often attain considerable dimensions; whilst Brachiopods, on the other hand, are few in number. Azvalves and Unzvalves are extremely plentiful ; and we meet here with the shells of Winged -Snails (Pteropods), belonging to such existing genera as /yalea (fig. 239) and C/odora. Lastly, the Cephalopods are represent- ed both by the chambered shells of Wautidi and by the internal skeletons of Cuttle- fishes (Spzrudirostra.) Bi ao ge views Ph rhe shell The Fishes of the Miocene MR ac Orbignyana, a Mocené period are very abundant, but of little special importance. Besides the remains of Bony Fishes, we meet in the marine deposits of this age with numerous pointed teeth belonging to different kinds of Sharks. Some of the genera of these— such as Carcharodon (fig. 241), Oxyrhina (fig. 240), Lamna, and Galeocerdo—are very widely distributed, ranging through — THE MIOCENE PERIOD. 313 both the Old and New Worlds ; and some of the species attain gigantic dimensions. Amongst the Amphibians we meet with distinctly modern types, such as Frogs (Rana) and Newts or Salamanders. The most celebrated of the latter is the famous Andrias Scheuchzert (fig. 242), dis- covered in the year 1725 in the fresh-water Miocene deposits of (Eéningen, in Switzerland. The skeleton indicates an animal nearly five feet in length; and it Fig. 240.—Tooth Fig. 241.—Tooth was originally described by OF ITE IER ORE apart Bie Scheuchzer, a Swiss physi- clan, in a dissertation published in 1731, as the remains of one of the human beings who were in existence at the time of the Noachian Deluge. Hence he applied to it the name of Homo diluvit testis. In reality, however, as shown by Cuvier, we have here the skeleton of a huge Newt, very closely allied to the Giant Salamander (J/Zenopfoma maxima) of Java. The remains of feftiles are far from uncommon in the Miocene rocks, consisting principally of Chelonians and Cro- codilians. ‘The Land-tortoises ( Zestudinide) make their first appearance during this period. The most remarkable form of this group is the huge Colossochelys Atlas of the Upper Miocene deposits of the Siwalik Hills in India, described by Dr Falconer and Sir Proby Cautley. Far exceeding any living ‘Tortoise in its dimensions, this enormous animal is estimated as having had a length of about twenty feet, measured from the tip of the snout to the extremity of the tail, and to have stood upwards of seven feet high. All the details of its organisation, however, prove that it must have been “ strictly a land animal, with herbivorous habits, and probably of the most inoffensive nature.” ‘The accomplished palzontologist just quoted, shows further that some of the traditions of the Hindoos would render it not improbable that this colossal Tortoise had survived into the earlier portion of the human period. Of the 4zvds of the Miocene period it is sufficient to re- mark that though specifically distinct, they belong, so far as known, wholly to existing groups, and therefore present no points of special palzeontolgical interest. The dZammatls of the Miocene are very numerous, and only ductus. Miocene. HISTORICAL PALZZONTOLOGY. 314 of the skeleton of Andrias Scheuchzeri. a Giant Salamander Tertiary of GEningen, in Switzerland. Reduced in size. —Front portion from the Miocene Fig. 242. THE’ MIOCENE PERIOD. 315 the more important forms can be here alluded to. Amongst the JZarsupials, the Old World still continued to possess species of Opossum (Didephys), allied to the existing American forms. The /dentates (Sloths, Armadillos, and Ant-eaters), at the present day mainly South American, are represented by two large European forms. One of these is the large AZacro- therium giganteum of the Upper Miocene of Gers in Southern France, which appears to have been in many respects allied to the existing Scaly Ant-eaters or Pangolins, at the same time that the disproportionately long fore-limbs would indicate that it possessed the climbing habits of the Sloths. The other is the still more gigantic Axcylotherium Pentelict of the Upper Miocene of Pikermé, which seems to have been as large as, or larger than, the Rhinoceros, and which must have been terres- trial in its habits. This conclusion is further borne out by the comparative equality of length which subsists between the fore and hind limbs, and is not affected by the curvature and crookedness of the claws, this latter feature being well marked in such existing terrestrial Edentates as the Great Ant-eater. The aquatic Sirenians and Cefaceans are represented in Miocene times by various forms of no special importance. Amongst the former, the previously existing genus Halithertum continued to survive, and amongst the latter we meet with remains of Dolphins and of Whales of the “ Zeuglodont” family. We may also note here the first appearance of true “Whalebone Whales,” two species of which, resembling the living “ Right Whale” of Arctic seas, and belonging to the same genus (Balena), have been detected in the Miocene beds of North America. The great order of the Ungulates or Hoofed Quadrupeds is very largely developed in strata of Miocene age, various new types of this group making their appearance here for the first time, whilst some of the characteristic genera of the preceding period are still represented under new shapes. Amongst the Odd-toed or “‘ Perissodactyle”’ Ungulates, we meet for the first time with representatives of the family RAznocertde compris- ing only the existing Rhinoceroses. In India in the Upper Miocene beds of the Siwalik Hills, and in North America, several species of Rhinoceros have been detected, agreeing with the existing forms in possessing three toes to each foot, and in having one or two solid fibrous “horns” carried upon the front of the head. On the other hand, the forms of this group which distinguish the Miocene deposits of Europe appear to have been for the most part hornless, and to have resembled the Tapirs in having three-toed hind-feet, but four-toed fore-feet. 316 HISTORICAL PALZONTOLOGY. The family of the Tapirs is represented, both in the Old and New Worlds, by species of the genus Zophiodon, some of which were quite diminutive in point of size, whilst others attained the dimensions of a horse. Nearly allied to this family, also, is the singular group of quadrupeds which Marsh has described from the Miocene strata of the United States under the name of Lrontotheride. ‘These extraordinary ani- mals, typified by Brontotherium (fig. 243) itself, agree with the fi Fig. 243.—Skull of Bronxtotherium ingens. Miocene Tertiary, United States. (4 \fter Marsh. ) existing Tapirs of South America and the Indian Archipelago in having the fore-feet four-toed, whilst the hind-feet are three- toed ; and a further point of resemblance is found in the fact (as shown by the form of the nasal bones) that the nose was long and flexible, forming a short movable proboscis or trunk, by means of which the animal was enabled to browse on shrubs or trees. They differ, however, from the Tapirs, not only in the apparent presence of a long tail, but also in the possession of a pair of very large “horn- -cores,” carried upon the nasal bones, indicating that the animal possessed horns of a similar structure to those of the “Hollow-horned” Rumin- ants (e.g., Sheep and Oxen). Brontotherium gigas is said to be nearly as large as an Elephant, whilst 2. zzgens appears to have attained dimensions still more gigantic. The well-known genus Zvtanotherium of the American Miocene would also appear to belong to this group. The family of the Horses (Zguide) appears under various forms in the Miocene, but the most important and best known of these is H/ifparion. In this genus the general conformation of the skeleton is extremely similar to ‘that of the existing Horses, and the external appearance of the animal must have been very much the same. The foot of Azpparion, however, THE MIOCENE PERIOD. aa7. as has been previously mentioned, differed from that of the Horse in the fact that whilst both possess the middle toe greatly developed and enclosed in a broad hoof, the former, in addition, possessed two lateral toes, which were sufficiently developed to carry hoofs, but were so far rudimentary that they hung idly by the side of the central toe without touching the ground (see fig. 230). In the Horse, on the other hand, these lateral toes, though present, are not only functionally useless, but are concealed beneath the skin. Remains of the Azpparion have been found in various regions in Europe and in India; and _ from the immense quantities of their bones found in certain localities, it may be safely inferred that these Middle Tertiary ancestors of the Horses lived, like their modern representa- tives, in great herds, and in open grassy plains or prairies. Amongst the Even-toed or Artiodactvle Ungulates, we for the first time meet with examples of the Wzppopotamus, with its four-toed feet, its massive body, and huge tusk-like lower canine teeth. The Miocene deposits of Europe have not hitherto yielded any remains of A7ppopotamus ; but several species have been detected in the Upper Miocene of the Siwalik Hills by Dr Falconer and Sir Proby Cautley. These ancient Indian forms, however, differ from the existing [/7ppopotamus amphibius of Africa in the fact that they possessed six incisor teeth in each jaw (fig. 244), whereas the latter has only four. Amongst the other Even-toed Ungulates, the family of the Pigs (Swzd¢a) is represented by true Swine (Sus Erymanthius), Peccaries (Dicotyles antiguus), and by forms which, like the great L/otherium of the American Miocene, have no represen- tative at the present day. The Upper Miocene of India has yielded examples of the Camels. Small Musk-deer (AmpAz- tragulus and Dremotherium) are known to have existed in France and Greece; and the true Deer (Cervide), with their solid bony antlers, appear for the first time here in the person of species allied to the living Stags (Cerzus), accompanied by the extinct genus Dorcatherium. The Giraffes (Camelopardalide), now confined to Africa, are known to have lived in India and Greece; and the allied Wel/adotherium, in some repects inter- mediate between the Giraffes and the Antelopes, ranged over Southern Europe from Attica to France. The great group of the ‘* Hollow-horned” Ruminants (Cavicornia), lastly, came into existence in the Miocene period; and though the typical families of the Sheep and Oxen are apparently wanting, there are true Antelopes, together with forms which, if systemati- cally referable to the Andzlopide, nevertheless are more or less clearly transitional between this and the family of the Sheep 316 HISTORICAL PALAONTOLOGY. and Goats. Thus the Paleoreas of the Upper Miocene of Greece may be regarded as a genuine Antelope; but the Fig. 244.—a, Skull of Hippopotamus Sivalensis, viewed from below, one-eighth of the natural size ; 4, Molar tooth of the same, showing the surface of the crown, one-half of the natural size; c, Front of the lower jaw of the same, showing the six incisors and the tusk-like canines, one-eighth of the natural size. Upper Miocene, Siwalik Hills. (After Falconer and Cautley.) Zragoceras of the same deposit is intermediate in its characters between the typical Antelopes and the Goats. Perhaps the most remarkable, however, of these Miocene Ruminants is the Stvatherium giganteum (fig. 245) of the Siwalik Hills, in India. In this extraordinary animal there were two pairs of horns, supported by bony “horn-cores,” so that there can be no hesitation in referring S7vatherium to the Cavicorn Rumin- ants. If all these horns had been simple, there would have been no difficulty in considering S7vatherium as simply a gigantic four-horned Antelope, essentially similar to the living Antilope (Tetraceros) guadricornis of India. The hinder pair of horns, however, is not only much larger than the front pair, but each possesses two branches or snags—a peculiarity not to be paralleled amongst any existing Antelope, save the abnormal Prongbuck (Antilocapra) of North America. Dr Murie, how- ever, in an admirable memoir on the structure and relationships THE MIOCENE PERIOD. 319 ' of Szvatherium, has drawn attention to the fact that the Prong- buck sheds the sheath of its horns annually, and has suggested Fig. 245.—Skull of Stvatherium giganteum, reduced in size. Miocene, India. (After Murie.) that this may also have been the case with the extinct form. This conjecture is rendered probable, amongst other reasons, by the fact that no traces of a horny sheath surrounding the horn-cores of the Indian fossil have been as yet detected. Upon the whole, therefore, we may regard the elephantine Stvatherium as being most nearly allied to the Prongbuck of Western America, and thus as belonging to the family of the Antelopes. It is to the Miocene period, again, to which we must refer the first appearance of the important order of the Elephants and their allies (fv oboscideans), all of which are characterised by their elongated trunk-like noses, the possession of five toes to the foot, the absence of canine teeth, the development of two or more of the incisor teeth into long tusks, and the adaptation of the molar teeth to a vegetable diet. Only three generic groups of this order are known—namely, the extinct Deno- therium, the equally extinct AZastodons, and the Elephants ; and all these three types are known to have been in existence as 320 HISTORICAL PALZONTOLOGY. early as the Miocene period, the first of them being exclusively confined to deposits of this age. Of the three, the genus Deinotherium is much the most abnormal in its characters ; so much so, that good authorities regard it as really being one of the Sea-cows (.Sévenéa)—though this view has been rendered untenable by the discovery of limb-bones which can hardly belong to any other animal, and which are distinctly Probosci- dean in type. The most celebrated skull of the Deinothere (fig. 246) is one which was exhumed from the Upper Miocene deposits of Epplesheim, in Hesse- Darmstadt, in the year 1836. This skull was four and a half feet in length, and indicated an animal larger than any existing species of Elephant. ‘The upper jaw is destitute of incisor or canine teeth, but is furnished on each side with five molars, which are opposed to a corresponding series of grinding teeth in the lower jaw. No canines are pre- sent in the lower jaw; but the , front portion of the jaw is ab- Fig. 246.—Skull of Detnotherium ruptly bent downwards, and car- giganteun, greatly reduced. From : : Bac the Upper Miocene of Germany. ries two huge tusk-like incisor teeth, which are curved down- wards and backwards, and the use of which is rather proble- matical. Not only does the Deinothere occur in Europe, but remains belonging to this genus have also been detected in the Siwalik Hills, in India. . The true Elephants (Z/ephas) do not appear to have ex- isted during the Miocene period in Europe, but several species have been detected in. the Upper Miocene deposits of the Siwalik Hills, in India. The fossil forms, though in all cases specifically, and in some cases even sub-generically, distinct, agree with those now in existence in the general conformation of their skeleton, and in the principal characters of their den- tition. In all, the canine teeth are wanting in both jaws; and there are no incisor teeth in the lower jaw, whilst there are two incisors in the front of the upper jaw, which are de- veloped into two huge “tusks.” There are six molar teeth on each side of both the upper and lower jaw, but only one, or at most a part of two, is in actual use at any given time ; and as this becomes worn away, it is pushed forward and replaced by its successor behind it. The molars are of THE MIOCENE PERIOD. 321 very large size, and are each composed of a number:of trans- verse plates of enamel united together by ivory; and by the Fig. 247.—A, Molar tooth of Zlephas planifrous, one-third of the natural size, show- ing the grinding surface—from the Upper Miocene of India; B, Profile view of the last upper molar of Mastodon Sivalensis, one-third of the natural size—from the Upper Miocene of India. (After Falconer.) process of mastication, the teeth become worn down to a flat surface, crossed by the enamel- ridges in varying patterns. These patterns are different in the “different species of Ele- phants, though constant for each; and they constitute one of the most readily available means of separating the fossil forms from one another. Of the seven Miocene Elephants of India, as judged by the characters of the molar teeth, two are allied to the existing Indian Elephant, one is related to the living African Elephant, and the remaining four are in some respects intermediate between the true Elephants and the Mastodons. The MMastodons, lastly, though quite elephantine in their x 322 HISTORICAL PALAZSONTOLOGY. general characters, possess molar teeth which have their crowns furnished with conical eminences or tubercles placed in pairs (fig. 247, B), instead of having the approximately flat surface characteristic of the grinders of the Elephants. As in the latter, there are two upper incisor teeth, which grow perma- nently during the life of the animal, and which constitute great tusks ; but the Mastodons, in addition, often possess two lower incisors, which in some cases likewise grow into small tusks. Three species of Jastodon are known to occur in the Upper Miocene of the Siwalik Hills of India; and the Miocene de- posits of the European area have yielded the remains of four species, of which the best known are the JZ. dongirostris and the M. angustidens. Whilst herbivorous Quadrupeds, as we have seen, were extremely abundant during Miocene times, and often attained gigantic dimensions, Beasts of Prey (Carnivora) were by no means wanting, most of the principal existing families of the order being represented in deposits of this age. Thus, we find aquatic Carnivores belonging to both the living groups of the Seals and Walruses ; true Bears are wanting, but their place is filled by the closely-allied genus Amphicyon, of which various species are known; Weasels and Otters were not unknown, and the Ayenictis and ILctitherium of the Upper Miocene of Greece are apparently intermediate between the Civet-cats and the Hyzenas ; whilst the great Cats of subsequent periods are more than adequately represented by the huge “‘ Sabre-toothed Tiger ” (AZachazrodus), with its immense trenchant and serrated canine teeth. : Amongst the Rodent Mammals, the Miocene rocks have yielded remains of Rabbits, Porcupines (such as the AZystrix primigenius of Greece), Beavers, Mice, Jerboas, Squirrels, and Marmots. All the principal living groups of this order were therefore differentiated in Middle Tertiary times. The Cheiroptera are represented by small insect-eating Bats; and the order of the Insectivorous Mammals is represented by Moles, Shrew-mice, and Hedgehogs. Lastly, the Monkeys (Quadrumana) appear to have existed during the Miocene period under a variety of forms, remains of these animals having been found both in Europe and in India ; but no member of this order has as yet been detected in the Miocene Tertiary of the North American continent. Amongst the Old World Monkeys of the Miocene, the two most interesting are the Pliopithecus and Dryopithecus of France. The former of these (fig. 248) is supposed to have been most nearly related to the living Semmnopitheci of Southern Asia, in THE PLIOCENE PERIOD. 323 which case it must have possessed a long tail. The JJesopz- thecus of the Upper Miocene of Greece is also one of the lower Fig. 248.—Lower jaw of Pliopithecus antiguus. Upper Miocene, France. Monkeys, as it is most closely allied to the existing Macaques. On the other hand, the Dryopithecus of the French Upper Miocene is referable to the group of the ‘‘ Anthropoid Apes,” and is most nearly related to the Gibbons of the present day, in which the tail is rudimentary and there are no cheek- pouches. Dryofpithecus was, also, of large size, equalling Man in stature, and apparently living amongst the trees and feed- ing upon fruits. CRAP TER xs LAE PLIGCENE! PERTOD: The highest division of the Tertiary deposits is termed the Pliocene formation, in accordance with the classification pro- posed by Sir Charles Lyell. ‘The Pliocene formations contaie from 40 to 95 per cent of existing species of JZo//usca, the re- mainder belonging to extinct species. ‘They.are divided by Sir Charles Lyell into two divisions, the Older Pliocene and Newer Pliocene. The Pliocene deposits of Britain occur in Suffolk, and are known by the name of “ Crags,” this being a local term used for certain shelly sands, which are employed in agriculture. Two of these Crags are referable to the Older Pliocene, viz., 324 HISTORICAL PALAZON TOLOGY. the White and Red Crags,—and one belongs to the Newer Pliocene, viz., the Norwich Crag. The White or Coralline Crag of Suffolk is the oldest of the Pliocene deposits of Britain, and is an exceedingly local for- mation, occurring in but a single small area, and having a maximum thickness of not more than 50 feet. It consists of soft sands, with occasional intercalations of flaggy limestone. Though of small extent and thickness, the Coralline Crag is of importance from the number of fossils which it contains. The name ‘ Coralline” is a misnomer; since there are few true Corals, and the so-called “ Corals” of the formation are really Folyzoa, often of very singular forms. ‘The shells of the Coral- line Crag are mostly such as inhabit the seas of temperate regions; but there occur some forms usually looked upon as indicating a warm climate. The Upper or Red Crag of Suffolk—like the Coralline Crag —has a limited geographical extent and a small thickness, rarely exceeding 40 feet. It consists of quartzose sands, usu- ally deep red or brown in colour, and charged with numerous fossils. Altogether more than 200 species of shells are known from the Red Crag, of which 60 per cent are referable to existing species. The shells indicate, upon the whole, a temperate or even cold climate, decidedly less warm than that indicated by the organic remains of the Coralline Crag. It appears, there- fore, that a gradual refrigeration was going on during the Pliocene period, commencing in the Coralline Crag, becoming intensified in the Red Crag, being still more severe in the Norwich Crag, and finally culminating in the Arctic cold of the Glacial period. Besides the A/ol/usca, the Red Crag contains the ear-bones of Whales, the teeth of Sharks and Rays, and remains of the Mastodon, Rhinoceros, and Tapir. The (ewer Pliocene deposits are represented in Britain by the Worwich Crag, a local formation occurring near Norwich. It consists of incoherent sands, loams, and gravels, resting in detached patches, from 2 to 20 feet in thickness, upon an eroded surface of Chalk. The Norwich Crag contains a mix- ture of marine, land, and fresh-water shells, with remains of fishes and bones of mammals; so that it must have been de- posited as a local sea-deposit near the mouth of an ancient river. It contains altogether more than roo marine shells, of which 89 per cent belong to existing species. Of the Mammals, the two most important are an Elephant (/ephas werwionalis), and the characteristic Phocene Mastodon (J/. THE PLIOCENE PERIOD. a2 Arvernensis), which is hitherto the only Mastodon found in Britain. According to the most recent views of high authorities, certain deposits—such as the so-called “ Bridlington Crag” of Yorkshire, and the ‘‘ Chillesford beds ” of Suffolk—are to be also included in the Newer Pliocene, upon the ground that they contain a small proportion of extinct shells. Our know- ledge, however, of the existing Molluscan fauna, is still so far incomplete, that it may reasonably be doubted if these sup- posed extinct forms have actually made their final disappear- ance, whilst the strata in question have a strong natural con- nection with the “ Glacial deposits,” as shown by the number of Arctic Mollusca which they contain. Here, therefore, these beds will be included in the Post-Phocene series, in spite of the fact that some of their species of shells are not known to exist at the present day. The following are the more important Pliocene deposits which have been hitherto recognised out of Britain:— t. In the neighbourhood of Antwerp occur certain “ crags,” which are the equivalent of the White and Red Crag in part. The lowest of these contains less than 50 per cent, and the highest 60 per cent, of existing species of shells, the remainder being extinct. 2. Bordering the chain of the Apennines, in Italy, on both sides is a series of low hills made up of Tertiary strata, which are known as the Sub-Apennine beds. Part of these is of Miocene age, part is Older Pliocene, and a portion is Newer Pliocene. The Older Phocene portion of the Sub-Apennines consists of blue or brown marls, which sometimes attain a thickness of 2000 feet. 3. In the valley of the Arno, above Florence, are both Older and Newer Pliocene strata. The former consist of blue clays and lignites, with an abundance of plants. The latter consist of sands and conglomerates, with remains of large Car- nivorous Mammals, Mastodon, Elephant, Rhinoceros, Hippo- potamus, &c. 4. In Sicily, Newer Pliocene strata are probably more largely developed than anywhere else in the world, rising sometimes to a height of 3000 feet above the sea. ‘The series consists of clays, marls, sands, and conglomerates, capped by a com- pact limestone, which attains a thickness of from 700 to 800 feet. The fossils of these beds belong almost entirely to living species, one of the commonest being the Great Scallop of the Mediterranean (Pecten Jacobeus). 5. Occupying an extensive area round the Caspian, Aral, 326 HISTORICAL PALAAONTOLOGY. and Azof Seas, are Pliocene deposits known as the “ Aralo- Caspian” beds. The fossils in these beds are partly fresh- water, partly marine, and partly intermediate in character, and they are in great part identical with species now inhabiting the Caspian. The entire formation appears to indicate the former existence of a great sheet of brackish water, forming an inland sea, like the Caspian, but as large as, or larger than, the Mediterranean. 6. In the United States, strata of Pliocene age are found in North and South Carolina. ‘They consist of sands and clays, with numerous fossils, chiefly JZolluscs and Lchinoderms. From 40 to 60 per cent of the fossils belong to existing species. On the Loup Fork of the river Platte, in the Upper Missouri region, are strata which are also believed to be refer- able to the Pliocene period, and probably to its upper division. They are from 300 to 400 feet thick, and contain land-shells, with the bones of numerous Mammals, such as Camels, Rhino- ceroses, Mastodons, Elephants, the Horse, Stag, &c. As regards the /ife of the Pliocene period, there are only two classes of organisms to which our attention need be directed—namely, the Shell-fish and the Mammals. So far as the former are concerned, we have to note in the first place that the introduction of new species of animals upon the globe went on rapidly during this period. In the Older Pliocene deposits, the number of shells of existing species is only from 40 to 60 per cent; but in the Newer Pliocene the pro- portion of living forms rises to as much as from 80 to 95 per cent. Whilst the Molluscs thus become rapidly mo- dernised, the Mammals still all belong to extinct species, though modern generic types gradually supersede the more antiquated forms of the Miocene. In the second place, there is good evidence to show that the Pliocene period was one in which the climate of the northern hemisphere underwent a gradual refrigeration. In the Miocene period, there is evi- dence to show that Europe possessed a climate very similar to that now enjoyed by the Southern United States, and cer- tainly very much warmer than it is at present. ‘The presence of Palm-trees upon the land, and of numerous large Cowries, Cones, and other shells of warm regions in the sea, sufficiently proves this. In the Older Pliocene deposits, on the other hand, northern forms predominate amongst the Shells, though some of the types of hotter regions still survive. In the Newer Pliocene, again, the Molluscs are such as almost exclusively inhabit the seas of temperate or even cold regions ; whilst if we regard deposits like the “ Bridlington Crag” and “ Chilles- THE PLIOCENE. PERIOD. 327 ford beds” as truly referable to this period, we meet at the close of this period with shells such as nowadays are distinct- ively characteristic of high latitudes. It might be thought that the occurrence of Quadrupeds such as the Elephant, Rhinoceros, and Hippopotamus, would militate against this generalisation, and would rather support the view that the climate of Europe and the United States must have been a hot one during the later portion of the Phocene period. We have, however, reason to believe that many of these extinct Mammals were more abundantly furnished with hair, and more adapted to withstand a cool temperature, than any of their living congeners. We have also to recollect that many of these large herbivorous quadrupeds may have been, and indeed probably were, more or less migratory in their habits ; and that whilst the winters of the later portion of the Pliocene period were cold, the summers might have been very hot. This would allow of a northward migration of such terrestrial animals during the summer-time, when there would be an ample supply of food and a suitably high temperature, and a southward recession towards the approach of winter. The chief palzontological interests of the Pliocene deposits, as of the succeeding Post-Pliocene, centre round the Mammals of the period ; and amongst the many forms of these we may restrict our attention to the orders of the Hoofed Quadrupeds (Ungulates), the Proboscideans, the Carnivora, and the Quad- vumana. Almost all the other Mammalian orders are more or less fully represented in Pliocene times, but none of them attains any special interest till we enter upon the Post-Pliocene. Amongst the Odd-toed Ungulates, in addition to the remains of true Tapirs (Zapirus Arvernensis), we meet with the bones of several species of Rhinoceros, of which the RAznoceros Etrius- cus and PR. megarhinus (fig. 249) are the most important. The former of these (fig. 249, A) derives its specific name from its abundance in the Pliocene deposits of the Val d’Arno, near Florence, and though principally Pliocene in its distribution, it survived into the earlier portion of the Post-Pliocene period. Rhinoceros Etruscus agreed with the existing African forms in having two horns placed one behind the other, the front one being the longest ; but it was comparatively slight and slender in its build, whilst the nostrils were separated by an incom- plete bony partition. In the RAznoceros megarhinus (fig. 249, B), on the other hand, no such partition exists between the nostrils, and the nasal bones are greatly developed in size. It was a two-horned form, and is found associated with Elephas meridionalis and £. antiguus in the Pliocene deposits of the 328 HISTORICAL PALAEONTOLOGY. Val d’Arno, near Florence. Like the preceding, it survived, in diminished numbers, into the earlier portion of the Post- Pliocene period. The Horses (Zgude@) are represented, both in Europe and Fig. 249.—A, Under surface of the skull of Rhinoceros Etruscus, one-seventh of the natural size—Pliocene, Italy ; B, Crowns of the three true molars of the upper jaw, left side, of Rhinoceros megarhinus (R. leptorhinus, Falconer), one-half of the natural size —Pliocene, France. (After Falconer.) America, by the three-toed Hipparions, which survive from the Miocene, but are now verging upon extinction. For the first time, also, we meet with genuine Horses (Zgwzs), in which each foot is provided with a single complete toe only, encased ina single broad hoof. One of the American species of this period (the gus excelsus) quite equalled the modern Horse in stature ; and it is interesting to note the occurrence of indi- genous horses in America at such a comparatively late geo- logical epoch, seeing that this continent certainly possessed none of these animals when first discovered by the Spaniards. Amongst the Even-toed Ungulates, we may note the occur- THE PLIOCENE PERIOD. 329 rence of Swine (Swzda), of forms allied to the Camels (Camed/- ide), and of various kinds of Deer (Cervide) ; but the most interesting Pliocene Mammal belonging to this section is the great Hippopotamus major of Britain and Europe. ‘This well- known species is very closely allied to the living Hippopotamus amphibius of Africa, from which it is separated only by its larger dimensions, and by certain points connected with the conformation of the skeleton. It is found very abundantly in the Pliocene deposits of Italy and France, associated with the remains of the Elephant, Mastodon, and Rhinoceros, and it survived into the earlier portion of the Post-Pliocene period. During this last-mentioned period, it extended its range north- wards, and is found associated with the Reindeer, the Bison, and other northern animals. From this fact it has been infer- red, with great probability, that the A/ppopotamus major was furnished with a long coat of hair and fur, thus differing from its nearly hairless modern representative, and resembling its associates, the Mammoth and the Woolly Rhinoceros. Passing on to the Phocene Proboscideans, we find that the great Deinotheria of the Miocene have now wholly disappeared, and the sole representatives of the order are Mastodons and Elephants. ‘The most important member of the former group is the Aastodon Arvernensis (fig. 250), which ranged widely Fig. 250.—Third milk-molar of the left side of the upper jaw of AZastodox Arvernensis, showing the grinding surface. Pliocene. over Southern Europe and England, being generally associated with remains of the Hlephas meridionalis, £. antiquus, Rhino- ceros megarhinus, and [Hippopotamus major. ‘The lower jaw seems to have been destitute of incisor teeth; but the upper incisors are developed into great tusks, which sometimes reach 330 HISTORICAL PALAOONTOLOGY. a length of nine feet, and which have the simple curvature of the tusks of the existing Elephants. Amongst the Pliocene Elephants the two most important are the Zvephas meridionalts and the Lvephas antiquus. Of these, the Lvlephas meridionalis (fig. 251) is found abundantly in the Pliocene deposits of a i. { { ) j j ! I/ ) / } i | j wW 3a \ a SAS wuss SSS 2S Fig. 251.—Molar tooth of Elephas meridionalis, one-third of the natural size. Pliocene and Post-Pliocene. Southern Europe and England, and also survived into the earlier portion of the Post-Pliocene period. Its molar teeth are of the type of those of the existing African Elephant, the spaces enclosed by the transverse enamel-plates being more or less lozenge-shaped, whilst the curvature of the tusks is simple. The £iephas antiguus (fig. 252) is very generally Fig. 252.—Molar tooth of Elephas antiguus, one-third of the natural size. Pliocene and Post-Pliocene. associated with the preceding, and it survived to an even later stage of the Post-Pliocene period. ‘The molar teeth are of the type of the existing Indian Elephant, with compara- tively thin enamel-ridges, placed closer together than in the African type ; whilst the tusks were nearly straight. Amongst the Pliocene Carnivores, we meet with true Bears (Ursus Arvernensis), Hyzenas (such as Hyena Hipparionum), and genuine Lions (such as the Fels angustus of North America); but the most remarkable of the beasts of prey of THE PLIOCENE PERIOD. 331 this period is the great “ Sabre-toothed Tiger” (AZachairodus), species of which existed in the earlier Miocene, and survived to the later Post-Pliocene. In this remarkable form we are presented with perhaps the most highly carnivorous type of all known beasts of prey. Not only are the jaws shorter in proportion even than those of the great Cats of the present day, but the canine teeth (fig. 253) are of enormous size, Big. 253.—A, Skull of Machairodus cultridens, without the lower jaw, reduced in size; B, Canine tooth of the same, one-half the natural size. Pliocene, France. greatly flattened so as to assume the form of a poignard, and having their margins finely serrated. Apart from the charac- ters of the skull, the remainder of the skeleton, so far as known, exhibits proofs that the Sabre-toothed Tiger was extraordi- narily muscular and powerful, and in the highest degree adapt- ed for a life of rapine. Species of Machairodus must have been as large as the existing Lion; and the genus is not only European, but is represented both in South America and in India, so that the geographical range of these predaceous beasts must have been very extensive. Lastly, we may note that the Pliocene deposits of Europe have yielded the remains of Monkeys (Quadrumana), allied to the existing Semnopithect and Macaques. 332 HISTORICAL PALZZVONTOLOGY. LITERATURE. The following list comprises a small selection of some of the more im- portant and readily accessible works and memoirs relating to the Tertiary rocks and their fossils. With few exceptions, foreign works relating to the Tertiary strata of the continent of Europe or their organic remains have been omitted :— (1) ‘Elements of Geology.’ Lyell. (2) ‘Students’ Elements of Geology.’ Lyell. (3) ‘Manual of Palzeontology.’ Owen. (4) ‘British Fossil Mammals and Birds.” Owen. (5) ‘Traité de Paléontologie.’ Pictet. (6) ‘Cours Elémentaire de Paléontologie.’ _D’Orbigny. (7) ‘* Probable Age of the London Clay,” &c.—‘ Quart. Journ. Geol. Soc.,’ vol. ii. Prestwich. (8) ‘Structure and Probable Age of the Bagshot Sands ’—Ibid., vol. iii. Prestwich. (9) ‘Tertiary Formations of the Isle of Wight ’—Ibid., vol. ii. Prest- wich. (10) ‘Structure of the Strata between the London Clay and the Chalk,’ &c.—Ibid., vols. vi., vili., and x. Prestwich. (11) ‘Correlation of the Eocene Tertiaries of England, France, and Belgium ’—Ibid., vol. xxvii. Prestwich. (12) ‘On the Fluvio-marine Formations of the Isle of Wight ’—Ibid., vol. ix. Edward Forbes. ; (13) ‘Newer Tertiary Deposits of the Sussex Coast’—Ibid., vol. xiii. Godwin- Austen. (14) ‘Kainozoic Formations of Belgium ’—Ibid., vol. xxii. Godwin- Austen. (15) ‘Tertiary Strata of Belgium and French Flanders ’—Ibid., vol. viii. Lyell. (16) ‘On Tertiary Leaf-beds in the Isle of Mull’—Ibid., vol. vii. The Duke of Argyll. (17) ‘Newer Tertiaries of Suffolk and their Fauna’—Ibid., vol. xxvi. Ray Lankester. (18) ‘Lower London Tertiaries of Kent’—Ibid., vol. xxii. Whitaker. (19) ‘*Guide to the Geology of London” — ‘Mem. Geol. Survey.’ Whitaker. (20) ‘Memoirs of the Geological Survey of Great Britain.’ (21) ‘Introductory Outline of the Geology of the Crag District’ (Sup- plement to Crag Mollusca, Paleeontographical Society). S. V. Wood, jun., and F. W. Harmer. (22) ‘*Tertiary Fluvio-marine Deposits of the Isle of Wight.” Edward Forbes. Edited by Godwin-Austen ; with Descriptions of the Fossils by Morris, Salter, and Rupert Jones—‘ Memoirs of the Geological Survey.’ (23) ‘Geological Excursions round the Isle of Wight.’ Mantell. (24) ‘Catalogue of British Fossils.’ Morris. (25) ‘Catalogue of Fossils in the Museum of Practical Geology.’ Ethe- ridge. (26) ‘Monograph of the Crag Polyzoa’ (Palzeontographical Society). Busk. (27) ‘Monograph of the Tertiary Brachiopoda’ (Ibid.) Davidson. (28) a es of the Tertiary Malacostracous Crustacea’ (Ibid.) Bell. THE PLIOCENE. PERIOD. e595 (29) ‘Monograph of the Tertiary Corals’ (Ibid.) Milne-Edwards and Haime. (30) ‘Supplement to the Tertiary Corals’ (Ibid.) Martin Duncan. (31) ‘ Monograph of the Eocene Mollusca’ (Ibid. ) Fred. E. Edwards. (32) ‘Monograph of the Eocene Mollusca’ (Ibid.) Searles V. Wood. (33) ‘ Monograph of the Crag Mollusca’ (Ibid.) Searles V. Wood. (34) ‘Monograph of the Tertiary Entomostraca’ (Ibid.) Rupert Jones. (35) ‘Monograph of the Foraminifera of the Crag’ (Ibid.) Rupert Jones, Parker, and H. B. Brady. (36)-‘ Monograph of the Radiaria of the London Clay’ (Ibid.) Edward Forbes. (37) ‘Monograph of the Cetacea of the Red Crag’ (Ibid.) Owen. (38) ‘Monograph of. the Fossil Reptiles of the London Clay’ (Ibid.) Owen and Bell. (39) **On the Skull of a Dentigerous Bird from the London Clay of Sheppey ”—‘ Quart. Journ. Geol. Soc.,’ vol. xxix. Owen. (40) ‘Ossemens Fossiles.’? Cuvier. (41) ‘Fauna Antiqua Sivalensis.’ Falconer and Sir Proby Cautley. ) ‘Palzeontological Memoirs.’ Falconer. ) § Animaux Fossiles et Géologie de PAttique.’ Gaudry. (44) ‘* Principal Characters of the Dinocerata”—‘ American Journ. of Science and Arts,’ vol. xi. Marsh. (45) * Principal Characters of the Brontotheridz’ (Ibid.) Marsh. (46) -‘ Principal Characters of the Tillodontia’ (Ibid.) Marsh. (47) ‘‘ Extinct Vertebrata of the Eocene of eee ”—* Geological Survey of Montana,’ &c., 1872. Cope. (48) *‘ Ancient Fauna of N ebraska”—‘ Smithsonian Contributions to Knowledge,’ vol. vi. Leidy. (49) ‘Manual of Geology.’ Dana. (50) ‘*Palzontology and Evolution” (Presidential Address to the Geological Society of London, 1870)— ‘Quart. Journ. Geol. Soc., Vol: xxvi: Huxley. (51) ‘Mineral Conchology.’ Sowerby. (52) ‘Description des Coquilles Fossiles,’ &c. Deshaye es. (53) ‘ Description des Coquilles Tertiaires de Belgique.’ Nyst. (54) ‘ Fossilen Polypen des Wiener Tertiar-beckens.’ Reuss. (55) ‘Paleeontologische Studien iiber die alteren Tertiar-schichten der Alpen.’ ‘Reuss, ) ‘Land und Siiss-wasser Conchylien der Vorwelt.’ Sandberger. ) ‘Flora Tertiaria Helvetica.’ Heer. (58) ‘Flora Fossilis Arctica.’ Heer. ) ‘Recherches sur le Climat et la Végéetation du Pays Tertiaire.. Heer. ) ‘Fossil Flora of Great Britain.’ Lindley and Hutton. (61) ‘Fossil Fruits and Seeds of the London Clay.’ Bowerbank. (62) ** Tertiary Leaf-beds of the Isle of Mull”—‘ Quart. Journ. Geol. Soc.,’ vol. vii. Edward Forbes. (63) ‘The Geology of England and Wales.’ Horace B. Woodward.* * This work—published whilst these sheets were going through the press—gives to the student a detailed view of all the strata of England and Wales, with their various sub- d:v:sions, from the base of the Paleozoic to the top of the Tertiary. 334 HISTORICAL PALZONTOLOGY. CHAPTER, SAL THE QUATERNARY PERIOD. THE PostT-PLIOCENE PERIOD. Later than any of the Tertiary formations are various de- tached and more or less superficial accumulations, which are generally spoken of as the ost-Zertiary formations, in accord- ance with the nomenclature of Sir Charles Lyell—or as the Quaternary formations, in accordance with the general usage of Continental geologists. In all these formations we meet with no Mollusca except such as are now alive—with the partial and very limited exception of some of the oldest de- posits of this period, in which a few of the shells occasionally belong to species not known to be in existence at the pre- sent day. Whilst the She//-jish of the Quaternary deposits are, generally speaking, identical with existing forms, the JZammads are sometimes referable to living, sometimes to extinct species. In accordance with this, the Quaternary formations are divided into two groups: (1) The fostPiiocene, in which the shells are almost invariably referable to existing species, but some of the Mammals are extinct ; and (2) the Recent, in which Zhe shells and the Mammals alike belong to existing species. The Post- Pliocene deposits are often spoken of as the Flecstocene forma- tions (Gr. Aleistos, most; ainos, new or recent), in allusion to the fact that the great majority of the living beings of this period belong to the species characteristic of the ‘‘ new” or Recent period. The Recent deposits, though of the highest possible interest, do not properly concern the palzontologist strictly so-called, but the zoologist, since they contain the remains of none but existing animals. They are “ Pre-historic,” but they belong entirely to the existing terrestrial order. The fost- Pliocene deposits, on the other hand, contain the remains of various extinct Mammals ; and though Man undoubtedly existed in, at any rate, the later portion of this period, if not through- out the whole of it, they properly form part of the domain of the paleontologist. The Post-Pliocene deposits are extremely varied, and very widely distributed ; and owing to the mode of their occurrence, the ordinary geological tests of age are in their case but very partially available. The subject of the classification of these THE QUATERNARY PERIOD. 355 deposits is therefore an extremely complicated one ; and as regards the age of even some of the most important of them, there still exists considerable difference of opinion. For our present purpose, it will be convenient to adopt a classifica- tion of the Post-Pliocene deposits founded on the relations which they bear in time to the great “ Ice-age” or “ Glacial period ;” though it is not pretended that our present know- ledge is sufficient to render such a classification more than a provisional one. In the early Tertiary period, as we have seen, the climate of the northern hemisphere, as shown by the Eocene animals and plants, was very much hotter than it is at present—partaking, indeed, of a sub-tropical character. In the Middle Tertiary or Miocene period, the temperature, though not so high, was still much warmer than that now enjoyed by the northern hemi- sphere ; and we know that the plants of temperate regions at this time flourished within the Arctic circle. In the later Tertiary or Pliocene period, again, there is evidence that the northern hemisphere underwent a further progressive diminu- tion of temperature ; though the climate of Europe generally seems at the close of the Tertiary period to have been if any- thing warmer, or at any rate not colder, than it is at the present day. With the commencement of the Quaternary period, however, this diminution of temperature became more de- cided ; and beginning with a temperate climate, we find the greater portion of the northern hemisphere to become gradu- ally subjected to all the rigours of intense Arctic cold. All the mountainous regions of Northern and Central Europe, of Britain, and of North America, became the nurseries of huge ice-streams, and large areas of the land appear to have been covered with a continuous ice-sheet. The Arcticconditions of this, the well-known “Glacial period,” relaxed more than once, and were more than once re-established with lesser intensity. Finally, a gradual but steadily progressive amelioration of tem- perature took place; the ice slowly gave way, and ultimately disappeared altogether; and the climate once more became temperate, except in high northern latitudes. The changes of temperature sketched out above took place slowly and gradually, and occupied the whole of the Post- Pliocene period. In each of the three periods marked out by these changes—in the early temperate, the central cold, and the later temperate period—certain deposits were laid down over the surface of the northern hemisphere; and these de- posits collectively constitute the Post-Pliocene formations. Hence we may conveniently classify all the accumulations of 3 36 HISTORICAL PALZONTOLOGY. this age under the heads of (1) Pre-Glacial deposits, (2) Glacial deposits, and (3) Post-Glacial deposits, according as they were formed before, during, or after the “ Glacial period.” It can- not by any means be asserted that we can definitely fix the precise relations in time of all the Post-Pliocene deposits to the Glacial period. On the contrary, there are some which hold a very disputed position as regards this point; and there are others which do not admit of definite allocation in this manner at all, in consequence of their occurrence in regions where no ‘Glacial Period” is known to have been established. For our present purpose, however, dealing as we shall have to do principally with the northern hemisphere, the above classifi- cation, with all its defects, has greater advantages than any other that has been yet proposed. I. Pre-GuaciaL Deposirs.—The chief pre-glacial deposit of Britain is found on the Norfolk coast, reposing upon the Newer Pliocene (Norwich Crag), and consists of an ancient land-sur- face which is known as the “Cromer Forest-bed.” This consists of an ancient soil, having embedded in it the stumps of many trees, still in an erect position, with remains of living plants, and the bones of recent and extinct quadru- peds. It is overlaid by fresh-water and marine beds, all the shells of which belong to existing species, and it is finally sur- mounted by true “glacial drift.” While all the shells and plants of the Cromer Forest-bed and its associated strata belong to existing species, the Mammals are partly living, partly ex- tinct. Thus we find the existing Wolf (Cavs /upus), Red Deer (Cervus elaphus), Roebuck (Cervus capreolus), Mole (Talpa Europea), and Beaver (Castor fiber), living in western England side by side with the “/7ppopotamus major, Elephas antiquus, Elephas meridionalis, Rhinoceros Etruscus, and R. megarhinus of the Pliocene period, which are not only extinct, but imply an at any rate moderately warm climate. Besides the above, the Forest-bed has yielded the remains of several extinct species of Deer, of the great extinct Beaver (Z7ogon- therium Cuvieri), of the Caledonian Bull or “ Urus” (Bos primigenius), and of a Horse (Zguus fossilis), little if at all distinguishable from the existing form. The so-called “ Bridlington Crag” of Yorkshire, and the ‘“‘Chillesford Beds” of Suffolk, are probably to be regarded as also belonging to this period; though many of the shells which they contain are of an Arctic character, and would indicate that they were deposited in the commencement of the Glacial period itself. Owing, however, to the fact that a few of the shells of these deposits are not known to occur in a living con- THE QUATERNARY PERIOD. 337 dition, these, and some other similar accumulations, are some- times considered as referable to the Pliocene period. If. GiactaL Deposirs.— Under this head is included a great series of deposits which are widely spread over both Europe and America, and which were formed at a time when the climate of these countries was very much colder than it is at present, and approached more or less closely to what we see at the present day in the Arctic regions. ‘These deposits are known by the general name of the Glacad deposits, or by the more specialised names of the Drift, the Northern Drift, the Boulder-clay, the Till, &ce. These glacial deposits are found in Britain as far south as the Thames, over the whole of Northern Europe, in all the more elevated portions of Southern and Central Europe, and over the whole of North America, as far south as the 39th parallel. They generally occur as sands, clays, and gravels, spread in widely-extended sheets over all the geological forma- tions alike, except the most recent, and are commonly spoken of under the general term of “ Glacial drift.” They vary much in their exact nature in different districts, but they universally consist of one, or all, of the following members :— 1. Unstratified clays, or loams, containing numerous angular or sub-angular blocks of stone, which have often been trans- ported for a greater or less distance from their parent rock, and which often exhibit polished, grooved, or striated surfaces. These beds are what is called Bouwlder-clay, or Til. 2. Sands, gravels, and clays, often more or less regularly stratified, but containing erratic blocks, often of large size, and with their edges wnuzworn, derived from considerable distances from the place where they are now found. In these beds it is not at all uncommon to find fossil shells; and these, though of existing species, are generally of an Arctic character, compris- ing a greater or Jess number of forms which are now exclusively found in the icy waters of the Arctic seas. These beds are often spoken of as “ Stratified Drift.” 3. Stratified sands and gravels, in which the pebbles are worn and rounded, and which have been produced by a re- ‘arrangement of ordinary glacial beds by the sea. ‘These beds are commonly known as “ Drift-gravels,” or ‘ Regenerated Drift.” Some of the last-mentioned of these are doubtless post- glacial ; but, in the absence of fossils, it is often impossible to arrive at a positive opinion as to the precise age of superficial accumulations of this nature. It is also the opinion of high authorities that a considerable number of the so-called “ cave- Y 338 HISTORICAL PALAZONTOLOGY. deposits,” with the bones of extinct Mammals, truly belong to the Glacial period, being formed during warm intervals when the severity of the Arctic cold had become relaxed. It is further believed that some, at any rate, of the so-called “ high- level” river-gravels and “ brick-earths” have likewise been deposited during mild or warm intervals in the great age of ice ; and in two or three instances this has apparently been demonstrated—deposits of this nature, with the bones of ex- tinct animals and the implements of man, having been shown to be overlaid by true Boulder-clay. The fossils of the undoubted Glacial deposits are principally shells, which are found in great numbers in certain localities, sometimes with Aoraminifera, the bivalved cases of Ostracode Crustaceans, &c. Whilst some of the shells of the “ Drift” are such as now live in the seas of temperate regions, others, as previously remarked, are such as are now only known to live in the seas of high latitudes ; and these therefore afford unquestionable evidence of cold conditions. Amongst these Arctic forms of shells which characterise the Glacial beds may be mentioned Pecten Islandicus (fig. 254), Pecten Gren- eve SOG al aN KAS Md os yy vy A PERS A OG) kf « Ry 3: ws 3 it ms Ay Aye 4 >. iy Ws Rel) Fi Ge ‘ M4 i CUT CARA GY YAY ORE fys 3333 Ps IN Warn = = f KY AR % 4%, Oi, 4 S ss % GM ij ai May eaadi (Util i cat UA ALA AM AMMAN Fig 254.—Left valve of Pecten Islandicus. Glacial and Recent. landicus, Scalaria Grenlandica, Leda truncata, Astarte borealis, Tellina proxima, Natica clausa, &c. III. Post-Guiacrat Deposirs.—As the intense cold of the Glacial period became gradually mitigated, and temperate THE QUATERNARY PERIOD. 339 conditions of climate were once more re-established, various deposits were formed in the northern hemisphere, which are found to contain the remains of extinct Mammals, and which, therefore, are clearly of Post-Pliocene age. To these deposits the general name of ost-Glacial formations is given ; but it is obvious that, from the nature of the case, and with our present limited knowledge, we cannot draw a rigid line of demarcation between the deposits formed towards the close of the Glacial period, or during warm “ interglacial” periods, and those laid down after the ice had fairly disappeared. Indeed it is ex- tremely improbable that any such rigid line of demarcation should ever have existed ; and it is far more likely that the Glacial and Post-Glacial periods, and their corresponding de- posits, shade into one another by an imperceptible gradation. Accepting this reservation, we may group together, under the general head of “ Post-Glacial Deposits,” most of the so-called ‘‘ Valley - gravels,” “ Brick - earths,” and ‘“‘ Cave - deposits,” to- gether with some ‘raised beaches” and various deposits of peat. ‘Though not strictly within the compass of this work, a few words may be said here as to the origin and mode of formation of the Brick-earths, Valley-gravels, and Cave- deposits, as the subject will thus be rendered more clearly intelligible. Every river produces at the present day beds of fine mud and loam, and accumulations of gravel, which it deposits at various parts of its course—the gravel generally occupying the lowest position, and the finer sands and mud coming above. Numerous deposits of a similar nature are found in most countries in various localities, and at various heights above ‘the present channels of our rivers. Many of these fluviatile (Lat. fluvius, a river) deposits consist of fine loam, worked for brick-making, and known as “ Brick-earths ;” and they have yielded the remains of numerous extinct Mammals, of which the Mammoth (Zdephas primigenius) is the most abundant. In the valley of the Rhine these fluviatile loams (known as “‘ Loess”) attain a thickness of several hundred feet, and con- tain land and fresh-water shells of existing species. With these occur the remains of Mammals, such as the Mammoth and Woolly Rhinoceros. Many of these Brick-earths are undoubtedly Post-Glacial, but others seem to be clearly ‘‘inter- glacial ;” and instances have recently been brought forward in which deposits of Brick-earth containing bones and shells of fresh-water Molluscs have been found to be overlaid by regu- lar unstratified boulder-clay. The so-called ‘ Valley-gravels,” like the Brick-earths, are 340 HISTORICAL PALAAONTOLOGY. fluviatile deposits, but are of a coarser nature, consisting of sands and gravels. Every river gives origin to deposits of this kind at different points along the course of its valley; and it is not uncommon to find that there exist in the valley of a single river two or more sets of these gravel-beds, formed by the river itself, but formed at times when the river ran at different levels, and therefore formed at different periods. These different accumulations are known as the “ high-level” and ‘‘ low-level” gravels; and a reference to the accompany- ing diagram will explain the origin and nature of these de- posits (fg. 255). When a river begins to occupy a particular Fig. 255.—Recent and Post-Pliocene Alluvial Deposits. 1, Peat of the recent period ; 2, Gravel of the modern river; 2’, Loam of the modern river; 3, Lower-level valley- gravel with bones of extinct Mammals (Post-Pliocene) ; 3’, Loam of the same age as 3; 4, Higher-level valley-gravel (Post-Pliocene); 4’, Loam of the same age as 4; 5, Upland gravels of various kinds (often glacial drift); 6, Older rocks. (After Sir Charles Lyell.) line of drainage, and to form its own channel, it will deposit fluviatile sands and gravels along its sides. As it goes on deepening the bed or valley through which it flows, it will deposit other fluviatile strata at a lower level beside its new bed. In this way have arisen the terms “high-level” and “low-level” gravels. We find, for instance, a modern river flowing through a valley which it has to a great extent or entirely formed itself; by the side of its immediate channel we may find gravels, sand, and loam (fig. 255, 2 2’) deposited by the river flowing in its present bed. These are recent fluviatile or alluvial deposits. At some distance from the present bed of the river, and at a higher level, we may find other sands and gravels, quite like the recent ones in charac- ter and origin, but formed at a time when the stream flowed at a higher level, and before it had excavated its valley to its present depth. These (fig. 255, 3 3’) are the so-called ‘‘ low- level gravels” of a river. At a still higher level, and still farther removed from the present bed of the river, we may find another terrace, composed of just the same materials as the lower one, but formed at a still earlier period, when the THE. QUATERNARY PERIOD. 341 excavation of the valley had proceeded to a much less extent. These (fig. 255, 4 4’) are the so-called “ Aigh-level gravels” of a river, and there may be one or more terraces of these. The important fact to remember about these fluviatile de- posits is this—that here the ordinary geological rule is reversed. The high-level gravels are, of course, the highest, so far as their actual elevation above the sea is concerned ; but geo- logically the lowest, since they are obviously much older than the low-level gravels, as these are than the recent gravels. How much older the high-level gravels may be than the low- level ones, it 1s impossible to say. They occur at heights varying from 10 to 100 feet above the present river-chan- nels, and they are therefore older than the recent gravels by the time required by the river to dig out its own bed to this depth. How long this period may be, our data do not enable us to determine accurately ; but if we are to calculate from the observed rate of erosion of the actually existing rivers, the period between the different valley-gravels must be a very long one. The lowest or recent fluviatile deposits which occur beside the bed of the present river, are referable to the Recent period, as they contain the remains of none but living Mammals. The two other sets of gravels are Post-Pliocene, as they contain the bones of extinct Mammals, mixed with land and fresh- water shells of existing species. Among the more important extinct Mammals of the low-level and high-level valley-gravels may be mentioned the Eilefhas antiquus, the Mammoth (£é- phas primigenius), the Woolly Rhinoceros (2. tichorhinus), the Hippopotamus, the Cave-lion, and the Cave-bear. Along with these are found unquestionable traces of the existence of Man, in the form of rude flint implements of undoubted human workmanship. The so-called ‘“ Cave - deposits,” again, though exhibiting peculiarities due to the fact of their occurrence in caverns or fissures in the rocks, are in many respects essentially similar to the older valley-gravels. Caves, in the great majority of instances, occur in limestone. When this is not the case, it will generally be found that they occur along lines of sea-coast, or along lines which can be shown to have anciently formed the coast-line. ‘There are many caves, however, in the making of which it can be shown that the sea has had no hand; and these are most of the caves of limestone districts. These owe their origin to the solvent action upon lime of water holding carbonic acid in solution. The rain which falls upon a lime- stone district absorbs a certain amount of carbonic acid from 342 HISTORICAL PALAZZONTOLOGY. the air, or from the soil. It then percolates through the rock, generally along the lines of jointing so characteristic of lime- stones, and in its progress it dissolves and carries off a certain quantity of carbonate of lime. In this way, the natural joints and fissures in the rock are widened, as can be seen at the present day in any or all limestone districts. By a continu- ance of this action for a sufficient length of time, caves may ultimately be produced. Nothing, also, is commoner in a limestone district than for the natural drainage to take the line of some fissure, dissolving the rock in its course. In this way we constantly meet in limestone districts with springs issuing from the limestone rock—sometimes as large rivers— the waters of which are charged with carbonate of lime, ob- tained by the solution of the sides of the fissure through which the waters have flowed. By these and similar actions, every district in which limestones are extensively developed will be found to exhibit a number of natural caves, rents, or fissures. The first element, therefore, in the production of cave-deposits, is the existence of a period in which limestone rocks were largely dissolved, and caves were formed in consequence of the then existing drainage taking the line of some fissure. Secondly, there must have been a period in which various deposits were accumulated in the caves thus formed. These cavern-deposits are of very various nature, consisting of mud, loam, gravel, or breccias of different kinds. In all cases, these materials have been introduced into the cave at some period subsequent to, or contemporaneous with, the formation of the cave. Sometimes the cave communicates with the surface by a fissure through which sand, gravel, &c., may be washed by rains or by floods from some neighbouring river. Sometimes the cave has been the bed of an ancient stream, and the de- posits have been formed as are fluviatile deposits at the surface. Or, again, the river has formerly flowed at a greater elevation than it does at present, and the cave has been filled with fluviatile deposits by the river at a time prior to the excava- tion of its bed to the present depth (fig. 256). In this last case, the cave-deposits obviously bear exactly the same rela- tion in point of antiquity to recent deposits, as do the low- level and high-level valley-gravels to recent river-gravels. In any case, it is necessary for the physical geography of the dis- trict to change to some extent, in order that the cave-deposits should be preserved. If the materials have been introduced by a fissure, the cave will probably become ultimately filled to the roof, and the aperture of admission thus blocked up. If ariver has flowed through the cave, the surface configura- THE QUATERNARY PERIOD. 343 tion of the district must be altered so far as to divert the river into a new channel. And if the cave is placed in the side of a river-valley, as in fig. 256, the river must have excavated Fig. 256.—Diagrammatic section across a river-valley and cave. aa, Recent valley- gravels near the channel (4) of the existing river; c, Cavern, partly filled with cave- earth; dd, High-level gravels, filling fissures in the ‘limestone, which perhaps communi- cate in some instances with the cave, and form a channel by which materials of various kinds were introduced into it; e e, Inclined beds of limestone. its channel to such a depth that it can no longer wash out the contents of the cave even in high floods. If the cave be entirely filled, the included deposits generally get more or less completely cemented together by the percola- tion through them of water holding carbonate of lime in solu- tion. If the cave is only partially filled, the dropping of water from the roof holding lime in solution, and its subsequent evaporation, would lead to the formation over the deposits below of a layer of stalagmite, perhaps several inches, or even feet, in thickness. In this way cave-deposits, with their con- tained remains, may be hermetically sealed up and preserved without injury for an altogether indefinite period of time. In all caves in limestone in which deposits containing bones are found, we have then evidence of three principal sets of changes. (1.) A period during which the cave was slowly hollowed out by the percolation of acidulated water ; (2.) A period in which the cave became the channel of an engulfed river, or otherwise came to form part of the general drainage- system of the district; (3.) A period in which the cave was inhabited by various animals. As a typical example of a cave with fossiliferous Post- Pliocene deposits, we may take Kent’s Cavern, near Torquay, in which a systematic and careful examination has revealed the following sequence of accumulations in descending order :— (z) Large blocks of limestone, which lie on the floor of the cave, having fallen from the roof, and which are sometimes cemented together by stalagmite. (4) A layer of black mould, from three to twelve inches thick, with human bones, fragments of pottery, stone and 344 HISTORICAL PALEONTOLOGY. bronze implements, and the bones of animals now living in Britain. ‘This, therefore, is a recent deposit. (c) A layer of stalagmite, from sixteen to twenty inches thick, but sometimes as much as five feet, containing the bones of Man, together with those of extinct Post-Pllocene Mammals. (7) A bed of red cave-earth, sometimes four feet in thick- ness, with numerous bones of extinct Mammals (Mammoth, Cave-bear, &c.), together with human implements of flint and horn. (ec) A second bed of stalagmite, in places twelve feet in thickness, with bones of the Cave-bear. (f) A red-loam and cave-breccia, with remains of the Cave- bear and human implements. The most important Mammals which are found in cave- deposits in Europe generally, are the Cave-bear, the Cave-lion, the Cave-hyzena, the Reindeer, the Musk-ox, the Glutton, and the Lemming—of which the first three are probably identical with existing forms, and the remainder are certainly so—to- gether with the Mammoth and the Woolly Rhinoceros, which are undoubtedly extinct. Along with these are found the implements, and in some cases the bones, of Man himself, in such a manner as to render it absolutely certain that an early race of men was truly contemporaneous in Western Europe with the animals above mentioned. IV. UNCLASSIFIED Post-PLIOCENE DeEposits.—Apart from any of the afore-mentioned deposits, there occur other accumu- lations—sometimes superficial, sometimes in caves—which are found in regions where a “ Glacial period” has not been fully demonstrated, or where such did not take place; and which, therefore, are not amenable to the above classification. The most important of these are known to occur in South America and Australia; and though their numerous extinct Mammalia place their reference to the Post-Pliocene period beyond doubt, their relations to the glacial period and its deposits in the northern hemisphere have not been precisely determined. CHAPTER “xeon THE POST-PLIOCENE PERIOD—Continued. As regards the /fe of the Post-Pliocene period, we have, in the first place, to notice the effect produced throughout the FAUNA OF THE POST-PLIOCENE. 345 northern hemisphere by the gradual supervention of the Glacial period. Previous to this the climate must have been temper- ate or warm-temperate ; but as the cold gradually came on, two results were produced as regards the living beings of the - area thus affected. In the first place, all those Mammals which, like the Mammoth, the Woolly Rhinoceros, the Lion, the Hyzena, and the Hippopotamus, require, at any rate, mode- rately warm conditions, would be forced to migrate southwards to regions not affected by the new state of things. In the second place, Mammals previously inhabiting higher latitudes, such as the Reindeer, the Musk-ox, and the Leniming, would be enabled by the increasing cold to migrate southwards, and to invade provinces previously occupied by the Elephant and the Rhinoceros. A precisely similar, but more slowly-executed process, must have taken place in the sea, the northern Mollus- ca moving southwards as the arctic conditions of the Glacial period became established, whilst the forms proper to temperate seas receded. As regards the readily locomotive Mammals, also, it is probable that this process was carried on repeatedly in a partial manner, the southern and northern forms alternately fluctuating backwards and forwards over the same area, in ac- cordance with the fluctuations of temperature which have been shown by Mr James Geikie to have characterised the Glacial period as a whole. We can thus readily account for the inter- mixture which is sometimes found of northern and southern types of Mammalia in the same deposits, or in deposits apparently synchronous, and within a single district. Lastly, at the final close of the arctic cold of the Glacial period, and the re-estab- lishment of temperate conditions over the northern hemisphere, a reversal of the original process took place—the northern Mammals retiring within their ancient limits, and the southern forms pressing northwards and reoccupying their original domains. The J/nvertebrate animals of the Post-Pliocene deposits re- quire no further mention—all the known forms, except a few of the shells in the lowest beds of the formation, being iden- tical with species now in existence upon the globe. The only point of importance in this connection has been previously noticed—namely, that in the true Glacial deposits themselves a considerable number of the shells belong to northern or Arctic types. As regards the Vertebrate animals of the period, no extinct forms of Fishes, Amphibians, or Reptiles are known to occur, but we meet with both extinct Birds and extinct Mammals. The remains of the former are of great interest, as indicating 340 HISTORICAL PALZONTOLOGY. the existence during Post- Pliocene times, at widely remote points of the southern hemisphere, of various wingless, and for the most part gigantic, Birds. All the great wingless Birds of the order Cwursores which are known as existing at the pres- ent day upon the globe, are restricted to regions which are either wholly or in great part south of the equator. ‘Thus the true Ostriches are African; the Rheas are South American ; the Emeus are Australian ; the Cassowaries are confined to Northern Australia, Papua, and the Indian Archipelago; the species of Apteryx are natives of New Zealand; and the Dodo and Solitaire (wingless, though probably not true Cwr- sores), both of which have been exterminated within histori- cal times, were inhabitants of the islands of Mauritius and Rodriguez, in the Indian Ocean. In view of these facts, it is noteworthy that, so far as known, all the Cursorial Birds of the Post-Pliocene period should have been confined to the same hemisphere as that inhabited by the living representatives of the order. It is still further interesting to notice that the extinct forms in question are only found in geographical prov- inces which are now, or have been within historical times, inhab- ited by similar types. The greater number of the remains of these have been discovered in New Zealand, where there now live several species of the curious wingless genus Afferyx ; and they have been referred by Professor Owen to several generic groups, of which Dzornis is the most important (fig. 257). Fourteen species of Dinornis have been described by the dis- tinguished palzontologist just mentioned, all of them being large wingless birds of the type of the existing Ostrich, having enormously powerful hind-lmbs adapted for running, but with the wings wholly rudimentary, and the breast-bone devoid of the keel or ridge which characterises this bone in all birds which fly. The largest species is the Dinornis giganteus, one of the most gigantic of living or fossil birds, the shank (tibia) measuring a yard in length, and the total height being at least ten feet. Another species, the Dinornis elephantopus (fig. 257), though not standing more than about six feet in height, was of an even more ponderous construction—‘“‘the framework of the skeleton being the most massive of any in the whole class of Birds,” whilst “ the toe-bones almost rival those of the Elephant” (Owen). The feet in Dznornis were furnished with three toes, and are of interest as presenting us with an un- doubted Bird big enough to produce the largest of the foot- prints of the Triassic Sandstones of Connecticut. New Zea- land has now been so far explored, that it seems questionable if it can retain in its recesses any living example of Dinornis ; FAUNA OF THE POST-PLIOCENE. 347 but it is certain that species of this genus were alive during the human period, and survived up to quite a recent date. Not only are the bones very numerous in certain localities, but Ai Mt Fig. 257.—Skeleton of Dinornzs elephantopus, greatly reduced. Post-Pliocene, New Zealand. (After Owen.) they are found in the most recent and superficial deposits, and they still contain a considerable proportion of animal matter; whilst in some instances bones have been found with the feathers attached, or with the horny skin of the legs still ad- hering to them. Charred bones have been found in connec- tion with native “‘ovens;” and the traditions of the Maories contain circumstantial accounts of gigantic wingless Birds, the “ Moas,” which were hunted both for their flesh and their plumage. Upon the whole, therefore, there can be no doubt 348 HISTORICAL PALAAON TOLOGY. but that the Moas of New Zealand have been exterminated at quite a recent period—perhaps within the last century—by the unrelenting pursuit of Man,—a pursuit which their wingless condition rendered them unable to evade. In Madagascar, bones have been discovered of another huge wingless Bird, which must have been as large as, or larger than, the Dinornis giganteus, and which has been described under the name of 4fiornis maximus. With the bones have been found eggs measuring from thirteen to fourteen inches in diameter, and computed to have the capacity of three Ostrich eggs. Atleast two other smaller species of fzornis have been described by Grandidier and Milne-Edwards as occurring in Madagascar; and they consider the genus to be so closely allied to the Dinornis of New Zealand, as to prove that these regions, now so remote, were at one time united byland. Unlike New Zealand, where there is the Apferyx, Madagascar is not known to possess any living wingless Birds ; but in the neighbouring island of Mauritius the wingless Dodo (Didus ineptus) has been exterminated less than three hundred years ago ; and the little island of Rodriguez, in the same geographical province, has in a similar period lost the equally wingless Solitaire (Pezophaps), both of these, however, being generally referred to the Fasores. The JZammats of the Post-Pliocene period are so numerous, that in spite of the many points of interest which they present, only a few of the more important forms can be noticed here, and that but briefly. The first order that claims our attention is that of the Marsupials, the headquarters of which at the present day is the Australian province. In Oolitic times Europe possessed its small Marsupials, and similar forms existed in the same area in the Eocene and Miocene periods ; but if size be any criterion, the culminating point in the history of the order was attained during the Post-Pliocene period in Australia. From deposits of this age there has been disen- tombed a whole series of re- mains of extinct, and for the most part gigantic, examples of this group of Quadrupeds. Not to speak of Wombats and Phalangers, two forms stand ae out prominently as represen- Fig. 258.—Skullof Diprotodon Australis, tatives of the Post-Pliocene animals of Australia. One of these is Diprotodon (fig. 258), representing, with many differ- ences, the well-known modern group of the Kangaroos. In FAUNAS OF ‘THE. POS?-PLIOCENE. 349 its teeth, Dzprofodon shows itself to be closely allied to the living, grass-eating Kangaroos; but the hind-limbs were not so disproportionately long. In size, also, Déprotodon must have many times exceeded the dimensions of the largest of its living successors, since the skull measures no less than three feet in length. The other form in question is Zhylacoleo (fig. 259), which is believed by Professor Owen to belong to the same group as the existing “‘ Native Devil” (Dasyurus) of Van Diemen’s Land, and therefore to have been flesh-eating and rapacious in its habits, though this view is not accepted by others. The principal feature in the skull of Zhy/acoleo is NN \W PATTI \\ ‘ j ss ri Uf Bez LZ WL Fig. 259.—Skull of Thylacoleo. Post-Pliocene, Australia. Greatly reduced. (After Flower.) the presence, on each side of each jaw, of a single huge tooth, which is greatly compressed, and has a cutting edge. ‘This tooth is regarded by Owen as corresponding to the great cut- ting tooth of the jaw of the typical Carnivores, but Professor Flower considers that 7ylacoleo is rather related to the Kan- garoo-rats. The size of the crown of the tooth in question is not less than two inches and a quarter ; and whether carnivo- rous or not, it indicates an animal of a size exceeding that of the largest of existing Lions. The order of the Zdentates, comprising the existing Sloths, Ant-eaters, and Armadillos, and entirely restricted at the present day to South America, Southern Asia, and Africa, is one alike 350 HISTORICAL PALAAONTOLOGY. singular for the limited geographical range of its members, their curious habits of life, and the well-marked peculiarities of their anatomical structure. South America is the metropo- lis of the existing forms ; and it is an interesting fact that there flourished within Post-Pliocene times in this continent, and to some extent in North America also, a marvellous group of ex- tinct Edentates, representing the living Sloths and Armadillos, but of gigantic size. ‘The most celebrated of these is the huge Megatherium Cuviert (fig. 260) of the South American Pampas. SS = Fig. 260.—Megatherium Cuvieri. Post-Pliocene, South America. The Megathere was a colossal Sloth-like animal which attained a length of from twelve to eighteen feet, with bones more mas- sive than those of the Elephant. Thus the thigh-bone is nearly thrice the thickness of the same bone in the largest of existing Elephants, its circumference at its narrowest point nearly equalling its total length; the massive bones of the shank (tibia and fibula) are amalgamated at their extremities ; the heel-bone (calcaneum) is nearly half a yard in length ; the haunch-bones (ilia) are from four to five feet across at their crests ; and the bodies of the vertebree at the root of the tail are from five to seven inches in diameter, from which it has been computed that the circumference of the tail at this part might have been from five to six feet. The length of the fore- foot is about a yard, and the toes are armed with powerful curved claws. It is known now that the Megathere, in spite of its enormous weight and ponderous construction, walked, like the existing Ant-eaters and Sloths, upon the outside edge of the fore-feet, with the claws more or less bent inwards FAUNA OF THE POST-PLIOCENE. 351 towards the palm of the hand. As in the great majority of the Edentate order, incisor and canine teeth are entirely wanting, the front of the jaws being toothless. The jaws, however, are furnished with five upper and four lower molar teeth on each side. These grinding teeth are from seven to eight inches in length, in the form of four-sided prisms, the crowns of which are provided with well-marked transverse ridges; and they continue to grow during the whole life of the animal. ‘There are indications that the snout was pro- longed, and more or less flexible; and the tongue was proba- bly prehensile. From the characters of the molar teeth it is certain that the Megathere was purely herbivorous in its habits ; and from the enormous size and weight of the body, it is equally certain that it could not have imitated its modern allies, the Sloths, in the feat of climbing, back downwards, amongst the trees. It is clear, therefore, that the Megathere sought its sustenance upon the ground ; and it was originally supposed to have lived upon roots. By a masterly piece of deductive reasoning, however, Professor Owen showed that this great ‘‘ Ground-Sloth” must have truly lived upon the foliage of trees, like the existing Sloths—but with this differ- ence, that instead of climbing amongst the branches, it actually uprooted the tree bodily. In this four de force, the animal sat upon its huge haunches and mighty tail, as on a tripod, and then grasping the trunk with its powerful arms, either wrenched it up by the roots or broke it short off above the ground. Marvellous as this may seem, it can be shown that every detail in the skeleton of the Megathere accords with the supposition that it obtained its food in this way. Similar habits were followed by the allied AZylodon (fig. 261), another of the great ‘‘ Ground-Sloths,” which inhabited South America during the Post-Pliocene period. In most respects, the JZ}/o- don is very like the Megathere; but the crowns of the molar teeth are flat instead of being ridged. The nearly-related genus AZegalonyx, unlike the Megathere, but like the Mylodon, extended its range northwards as far as the United States. Just as the Sloths of the present day were formerly repre- sented in the same geographical area by the gigantic Megathe- roids, so the little banded and cuirassed Armadillos of South America were formerly represented by gigantic species, con- stituting the genus Glyptodon. The Glyptodons (fig. 262) differed from the living Armadillos in having no bands in their armour, so that they must have been unable to roll themselves up. It is rare at the present day to meet with any Armadillo over two or three feet in length; but the length of 352 HISTORICAL PALZONTOLOGY. the Glyptodon clavipes, from the tip of the snout to the end of the tail, was more than nine feet. There are no canine or incisor teeth in the Glyptodon, but Fig. 261.—Skeleton of M/ylodon robustus. Post-Pliocene, South America. there are eight molars on each side of each jaw, and the crowns of these are fluted and almost trilobed. ‘The head is covered Fig. 262.—Skeleton of Glyptodon clavipes. Post-Pliocene, South America. by a helmet of bony plates, and the trunk was defended by an armour of almost hexagonal bony pieces united by sutures, and FAUNA OF THE POST-PLIOCENE. 353 exhibiting special patterns of sculpturing in each species. The tail was also defended by a similar armour, and the vertebrz were mostly fused together so as to form a cylindrical bony rod. In addition to the above-mentioned forms, a number of other Edentate animals have been discovered by the re- searches of M. Lund in the Post-Pliocene deposits of the Brazilian bone-caves. Amongst these are true Ant-eaters, Armadillos, and Sloths, many of them of gigantic size, and all specifically or generically distinct from existing forms. Passing over the aquatic orders of the Szrenzans and Ce- taceans, we come next to the great group of the Hoofed Quad- rupeds, the remains of which are very abundant in Post- Pliocene deposits both in Europe and North America. Amongst the Odd-toed Ungulates the most important are the Rhinoceroses, of which three species are known to have existed in Europe during the Post-Pliocene period. Two of these are the well-known Pliocene forms, the AR/Aznoceros Etruscus and the R. megarhinus, still surviving in diminished numbers; but the most famous is the RAznoceros tichorhinus (fig. 263), or so-called ‘‘ Woolly Rhinoceros.” This species Fig. 263.—Skull of the Tichorhine Rhinoceros, the horns being wanting. One-tenth of the natural size. Post-Pliocene deposits of Europe and Asia. is known not only by innumerable bones, but also by a car- cass, at the time of its discovery complete, which was found embedded in the frozen soil of Siberia towards the close of last century, and which was partly saved from destruction by _ the exertions of the naturalist Pallas. From this, we know that the Tichorhine Rhinoceros, like its associate the Mam- moth, was provided with a ccating of hair, and therefore was enabled to endure a more severe climate than any existing Zz 354 HISTORICAL PALEONTOLOGY. species. The skin was not thrown into the folds which char- acterise most of the existing forms; and the technical name of the species refers to the fact that the nostrils were com- pletely separated by a bony partition. The head carried two horns, placed one behind the other, the front one being un- usually large. As regards its geographical range, the Woolly Rhinoceros is found in Europe in vast numbers north of the Alps and Pyrenees, and it also abounded in Siberia; so that it would appear to be a distinctly northern férm, and to have been adapted for a temperate climate. It is not known to occur in Pliocene deposits, but it makes its first appearance in the Pre-Glacial deposits, surviving the Glacial period, and being found in abundance in Post-Glacial accumulations. It was undoubtedly a contemporary of the earlier races of men in Western Europe ; and it may perhaps be regarded as being the actual substantial kernel of some of the “ Dragons” of fable. The only other Odd-toed Ungulate which needs notice is the so-called Lguus fosstlis of the Post-Phocene of Europe. This made its appearance before the Glacial period, and ap- pears to be in reality identical with the existing Horse (Zguus caballus). ‘True Horses also occur in the Post-Pliocene of North America; but, from some cause or another, they must have been exterminated before historic times. Amongst the Even-toed Ungulates, the great A77ppopotamus major of the Pliocene still continued to exist in Post-Pliocene times in Western Europe; and the existing Wild Boar (Sus scrofa), the parent of our domestic breeds of Pigs, appeared for the first time. The Old World possessed extinct repre- sentatives of its existing Camels, and lost types of the living Llamas inhabited South America. Amongst the Deer, the Post- Pliocene accumulations have yielded the remains of various living species, such as the Red Deer (Cervus elaphus), the Reindeer (Cervus tarandus), the Moose or Elk (A/lces malchis), and the Roebuck (Cervus capreolus), together with a number of extinct forms. Among the latter, the great “Trish Elk” (Cervus megaceros) is justly celebrated both for its size and for the number and excellent preservation of its discovered remains. ‘This extinct species (fig. 264) has been found principally in peat-mosses and Post-Plocene lake- deposits, and is remarkable for the enormous size of the spreading antlers, which are widened out towards their ex- tremities, and attain an expanse of over ten feet from tip to tip. It is not a genuine Elk, but is intermediate between the Reindeer and the Fallow-deer. Among the existing Deer FAUNA OF THE POST-PLIOCENE. 355 of the Post-Pliocene, the most noticeable is the Reindeer, an essentially northern type, existing at the present day in Fig. 264.—Skeleton of the “ Trish Elk” (Ceruzs megaceros). Post-Pliocene, Britain. Northern Europe, and also (under the name of the “ Caribou”) in North America. When the cold of the Glacial period be- came established, this boreal species was enabled to invade Central and Western Europe in great herds, and its remains are found abundantly in cave-earths and other Post-Pliocene deposits as far south as the Pyrenees. In addition to the above, the Post-Pliocene deposits of Europe and North America have yielded the remains of vari- ous Sheep and Oxen. One of the most interesting of the 356 HISTORICAL PALZZONTOLOGY. latter is the “ Urus” or Wild Bull (Bos primigenius, fig. 265), which, though much larger than any of the existing forms, is Fig. 265.—Skull of the Urus (Bos primigenius). Post-Pliocene and Recent. (After Owen.) believed to be specifically undistinguishable from the domes- tic Ox (Bos taurus), and to be possibly the ancestor of some of the larger European varieties of oxen. In the earlier part of its existence the Urus ranged over Europe and Britain in company with the Woolly Rhinoceros and the Mammoth; but it long survived these, and does not appear to have been finally exterminated till about the twelfth century. Another remarkable member of the Post-Phocene Cattle, also to be- gin with an associate of the Mammoth and Rhinoceros, is the European Bison or “ Aurochs” (Lzson priscus). This “maned” ox formerly abounded in Europe in Post-Glacial times, and was not rare even in the later periods of the Roman empire, though much diminished in numbers, and driven back into the wilder and more inaccessible parts of the country. At present this fine species has been so nearly exterminated that it no longer exists in Europe save in Lithuania, where its preservation has been secured by ngid protective laws. Lastly, the Post- Pliocene deposits have yielded the remains of the singular living animal which is known as the Musk-ox or Musk-sheep (Ovibos moschatus). At the present day, the Musk-ox is an inhabitant of the “barren grounds” of Arctic America, and it is remarkable for the great length of its hair. It is, like the Reindeer, a dis- FAUNA OF THE POST-PLIOCENE: 357 tinctively northern animal ; but it enjoyed during the Glacial period a much wider range ‘than it has at the present day, the conditions suitable for its existence being then extended over: a considerable portion of the northern. hemisphere. Thus remains of the Musk-Ox are found in greater or less abun- dance in Post-Pliocene deposits over a great part of Europe, extending even to the south of France; and closely- related forms are found in similar deposits in the United States. Coming to the Proboscideans, we find that the Mastodons seem to have disappeared in Europe at the close of the Phocene period, or at the very commencement of the Post- Pliocene. In the New World, on the other hand, a species of Mastodon (AZ. Americanus or M. Ohioticus) is found abun- dantly in deposits of Post-Plocene age, from Canada to Texas. . Very perfect skeletons of this species have been exhumed from morasses and swamps, and large individuals attained a length (exclusive of the tusks) of seventeen feet and a height of eleven feet, the tusks being twelve feet in length. Remains of Lilephants are also abundant i in the Post- Pliocene deposits of both the Old and the New World. Amongst these, we find in Europe the two familiar Pliocene species EB pert- dionalis and £. antiguwus still surviving, but in diminished numbers. With these are found in vast abundance the re- mains of the characteristic Elephant of the Post-Pliocene, the well-known “ Mammoth” (Ziephas primigenius), which is ac- companied in North America by the nearly-allied, but more southern species, the Llephas Americanus. ‘The Mammoth (fig. 266) is considerably larger than the largest of the living Ele- phants, the skeleton being over sixteen feet in length, exclusive of the tusks, and over nine feet in height. The tusks are bent almost into a circle, and are sometimes twelve feet in length, measured along their curvature. In the frozen soil of Siberia several carcasses of the Mammoth have been discovered with the flesh and skin still attached to the bones, the most cele- brated: of these being a Mammoth which was discovered at the beginning of this century at the mouth of the Lena, on the borders of the Frozen Sea, and the skeleton of which is now preserved at St Petersburg (fig. 266). From the occurrence of the remains of the Mammoth in vast numbers in Siberia, it might have been safely inferred that this ancient Elephant was able to endure a far more rigorous climate than its existing congeners. This infer- ence has, however, been rendered a certainty by the specimens just referred to, which show that the Mammoth was protected against the cold by a thick coat of reddish-brown wool, some nine or ten inches long, interspersed with strong, coarse black 358 HISTORICAL PALAEONTOLOGY. hair more than a foot in length. The teeth of the Mammoth (fig. 267) are of the type of those of the existing Indian Ele- phant, and are found in immense numbers in certain localities. Post-Pliocene. Portions of the integument still adhere les is still attached to the feet. —Skeleton of the Mammoth (Zlephas primigenius). to the head, and the thick skin of the so Fig. 266. The Mammoth was essentially northern in its distribution, never passing south of a line drawn through the Pyrenees, the Alps, the northern shores of the Caspian, Lake Baikal, Kam- FAUNA OF THE POST-PLIOCENE. 359 schatka, and the Stanovi Mountains (Dawkins): It occurs in the Pre-Glacial forest-bed of Cromer in Norfolk, survived the Fig. 267.—Molar tooth of the Mammoth (Elefhas primigenius), upper jaw, right side, one-third of the natural size. a, Grinding surface; 4, Side view. Post- Pliocene. Glacial period, and is found abundantly in Post-Glacial de- posits in France, Germany, Britain, Russia in Europe, Asia, and North America, being often associated with the Reindeer, Lemming, and Musk-ox. That it survived into the earlier portion of the human period is unquestionable, its remains having been found in a great number of instances associated with implements of human manufacture ; whilst in one instance a recognisable portrait of it has been discovered, carved on bone. Amongst other Elephants which occur in Post-Pliocene de- posits may be mentioned, as of special interest, the pigmy Elephants of Malta. One of these—the Alephas Melitensts, or so-called ‘‘ Donkey-Elephant”—was not more than four and a half feet in height. The other—the Lvephas Falconeri, of Busk—was still smaller, its average height at the withers not exceeding two and a half to three feet. Whilst herbivorous animals abounded during the Post- Pliocene, we have ample evidence of the coexistence with them of a number of Carnivorous forms, both in the New and the Old World. The Bears are represented in Europe by at least three species, two of which—namely, the great Grizzly Bear (Ursus ferox) and the smaller Brown Bear (Ursus arctos) —are in existence at the present day. The third speciesis the 360 HISTORICAL PALAZONTOLOGY. celebrated Cave-bear (Ursus speleus, fig. 268), which is now extinct. The Cave-bear exceeded in its dimensions the largest Fig. 268.—Skull of Ursus sfeleus. Post-Pliocene, Europe. One-sixth of the natural size. of modern Bears; and its remains, as its name implies, have been found mainly in cavern-deposits. Enormous numbers of this large and ferocious species must have lived in Europe in Post-Glacial times; and that they survived into the human period, is clearly shown by the common association of their bones with the implements of man. ‘They are occasionally accompanied by the remains of a Glutton (the Guo speleus), which does not appear to be really separable from the existing Wolverine or Glutton of northern regions (the Gzlo luscus). In addition, we meet with the bones of the Wolf, Fox, Weasel, Otter Badger, Wild Cat, Panther, Hyzena, and Lion, &c., together with the extinct JZachairodus or ‘‘ Sabre - toothed Tiger.” The only two of these that deserve further mention are the Hyzna and the Lion. The Cave-hyzena (Hyena spelea, fig. 269) is regarded by high authorities as nothing more than a variety of the living Spotted Hyzna ( crocuta) of South Africa. This well-known species inhabited Britain and a considerable portion of Europe during a large part of the Post-Pliocene period ; and its remains often occur in great . abundance. Indeed, some caves, such as the Kirkdale Cavern in Yorkshire, were dens inhabited during long periods by these animals, and thus contain the remains of numerous individuals and of successive generations of Hyzenas, together with in- numerable gnawed and bitten bones of their prey. ‘That the Cave-hyzena was a contemporary with Man in Western Europe during Post-Glacial times is shown beyond a doubt by the common association of its bones with human implements. FAUNA OF THE POST-PLIOCENE. 301 Lastly, the so-called Cave-lion (é/is spelea), long supposed to be a distinct species, has been shown to be nothing more Fig. 269.—Skull of Hyena sfelea, one-fourth of the natural size, Post-Pliocene, Europe. than a large variety of the existing Lion (Fes /o). This animal inhabited Britain and Western Europe in times pos- terior to the Glacial period, and was a contemporary of the Cave-hyzena, Cave-bear, Woolly Rhinoceros, and Mammoth. The Cave-lion also unquestionably survived into the earlier portion of the human period in Europe. The Post-Pliocene deposits of Europe have further yielded the remains of numerous Aodents—such as the Beaver, the Northern Lemming, Marmots, Mice, Voles, Rabbits, &c.—to- gether with the gigantic extinct Beaver known as the Zvogon- therium Cuviert (fig. 270). The great Castoroides Ohtoensis of the Post-Pliocene of North America is also a great ex- tinct Beaver, which reached a length of about five feet. Lastly, the Brazilian bone- caves have yielded the re- mains of numerous Rodents of types now characteristic of South America, such as Guinea-pigs, Capybaras, tree. (08 775. founth ofthe naturalsizes Post inhabiting Porcupines, and Pliocene, Britain. Coypus. The deposits just alluded to have further yielded the remains of various Monkeys, such as Howling Monkeys, Squirrel Monkeys, and Marmosets, all of which belong to the eroup of Quadrumana which is now exclusively confined to 362 HISTORICAL PALZONTOLOGY. the South American continent — namely, the “ Platyrhine” Monkeys. We still have very briefly to consider the occurrence of Man in Post-Pliocene deposits ; but before doing so, it will be well to draw attention to the evidence afforded by the Post- Pliocene Mammals as to the climate of Western Europe at this period. The chief point which we have to notice is, that a considerable revolution of opinion has taken place on this point. It was originally believed that the presence of such animals as Elephants, Lions, the Rhinoceros, and the Hippo- potamus afforded an irrefragable proof that the climate of Europe must have been a warm one, at any rate during Post- Glacial times. The existence, also, of numbers of Mammoths: in Siberia, was further supposed to indicate that this high tem- perature extended itself very far north. Upon the whole, how- ever, the evidence is against this view. Not only is there great difficulty in supposing that the Arctic conditions of the Glacial period were immediately followed by anything warmer than a cold-temperate climate; but there is nothing in the nature of the Mammals themselves which would absolutely forbid their living ina temperate climate. The zppofotamus major, though probably clad in hair, offers some difficulty—since, as pointed out by Professor Busk, it must have required a climate suffi- ciently warm to insure that the rivers were not frozen over in the winter; but it was probably a migratory animal, and its occur- rence may be accounted for by this. The Woolly Rhinoceros and the Mammoth are known with certainty to have been pro- tected with a thick covering of wool and hair; and their ex- tension northwards need not necessarily have been limited by anything except the absence of a sufficiently luxuriant vege- tation to afford them food. The great American Mastodon, though not certainly known to have possessed a hairy covering, has been shown to have lived upon the shoots of Spruce and Firs, trees characteristic of temperate regions—as shown by the undigested food which has been found with its skeleton, oc- cupying the place of the stomach. The Lions and Hyeenas, again, as shown by Professor Boyd Dawkins, do not indicate necessarily a warm climate. Wherever a sufficiency of her- bivorous-animals to supply them with food can live, there they can live also; and they have therefore no special bearing upon the question of climate. After a review of the whole evidence, Professor Dawkins concludes that the nearest approach at the present day to the Post-Pliocene climate of Western’ Europe is to be found in the climate of the great Siberian plains which stretch from the Altai Mountains to the Frozen Sea. ‘Covered FAUNA OF THE POST-PLIOCENE. 363 by impenetrable forests, for the most part of Birch, Poplar, Larch, and Pines, and low creeping dwarf Cedars, they present every gradation in climate from the temperate to that in which the cold is too severe to admit of the growth of trees, which decrease in size as the traveller advances northwards, and are replaced by the grey mosses and lichens that cover the low marshy ‘tundras.’ —The maximum winter cold, registered by Admiral Von Wrangel at Nishne Kolymsk, on the banks of the Kolyma, is—65° in January. ‘Then breathing becomes difficult ; the Reindeer, that citizen of the Polar region, with- draws to the deepest thicket of the forest, and stands there motionless as if deprived of life ;’? and trees burst asunder with the cold. Throughout this area roam Elks, Black Bears, Foxes, Sables, and Wolves, that afford subsistence to the Jakutian and Tungusian fur-hunters. In the northern part countless herds of Reindeer, Elks, Foxes, and Wolverines make up for the poverty of vegetation by the rich abundance of animal life. ‘Enormous flights of Swans, Geese, and Ducks arrive in the spring, and seek deserts where they may moult and build their nests in safety. Ptarmigans run in troops amongst the bushes; little Snipes are busy along the brooks and in the morasses ; the social Crows seek the neighbourhood of new habitations ; and when the sun shines in spring, one may even sometimes hear the cheerful note of the Finch, and in autumn that of the Thrush.’ Throughout this region of woods, a hardy, middle-sized breed of horses lives under the mastership and care of man, and is eminently adapted to bear the severity of the climate. . . . The only limit to their northern range is the difficulty of obtaining food. The severity of the winter through the southern portion of this vast wooded area is almost compensated for by the summer heat and its marvellous effect on vegetation.”—(Dawkins, ‘Monograph of Pleistocene Mammalia.’) Finally, a few words must be said as to the occurrence of the remains of Man in Post-Pliocene deposits. That Man existed in Western Europe and in Britain during the Post-Pliocene period, is placed beyond a doubt by the occurrence of his bones in deposits of this age, along with the much more frequent occurrence of implements of human manufacture. At what precise point of time during the Post-Pliocene period he first made his appearance is still a matter of conjecture. Recent researches would render it probable that the early inhabitants of Britain and Western Europe were witnesses of the stupend- ous phenomena of the Glacial period ; but this cannot be said - to have been demonstrated. That Man existed in these 304 HISTORICAL PALAAONTOLOGY. regions during the Post-Glacial division of Post-Plocene time cannet be doubted fora moment. As to the physical peculi- arities of the ancient races that lived with the Mammoth and the Woolly Rhinoceros, little is known compared with what we may some day hope to know. Such information as we have, however, based principally on the skulls of the Engis, Neanderthal, Cro-Magnon, and Bruniquel caverns, would lead to the conclusion that Post-Plocene Man was in no respect inferior in his organisation to, or less highly developed than, many existing races. All the known skulls of this period, with the single exception of the Neanderthal cranium, are in all respects average and normal in their characters ; and even the Neanderthal skull possessed a cubic capacity at least equal to that of some existing races. The implements of Post-Phocene Man are exclusively of stone or bone; and the former are invariably of rude shape and wzdressed. ‘These “ palzeolithic ” tools (Gr. palaios, ancient ; “thos, stone) point to a very early condition of the arts; since the men of the earlier portion of the Recent period, though likewise unacquainted with the metals, were in the habit of polishing or dressing the stone implements which they fabricated. It is impossible here to enter further into this subject ; and it would be useless to do so without entering as well into a consideration of the human remains of the Recent period—a period which lies outside the province of the present work. So far as Post-Pliocene Man is concerned, the chief points which the paleontological student has to remember have been else- where summarised by the author as follows :— 1. Man unquestionably existed during the later portion of what Sir Charles Lyell has termed the ‘‘ Post-Pliocene” period. In other words, Man’s existence dates back to a time when several remarkable Mammals, previously mentioned, had not yet become extinct; but he does not date back to a time anterior to the present J/Zo/luscan fauna. 2. The antiquity of the so-called Post-Pliocene period is a matter which must be mainly settled by the evidence of Geology proper, and need not be discussed here. 3. The extinct Mammals with which man coexisted in Western Europe are mostly of large size, the most important being the Mammoth (£vephas primigenius), the Woolly Rhino- ceros (Rhinoceros tichorhinus), the Cave-lion (Fis spelea), the Cave-hyzena (Hyena spelea), and the Cave-bear ( Ursus speleus). We do not know the causes which led to the extinction of these Mammals; but we know that hardly any Mammalian species has become extinct during the historical period. FAUNA OF THE. POST-PLIOCENE. 305 4. The extinct Mammals with which man coexisted are re- ferable in many cases to species which presumably required a very different climate to that now prevailing in Western Europe. How long a period, however, has been consumed in the bring- ing about of the climatic changes thus indicated, we have no means of calculating with any approach to accuracy. 5. Some of the deposits in which the remains of man have been found associated with the bones of extinct Mammals, are such as to show incontestably that great changes in the phy- sical geography and surface-configuration of Western Europe have taken place since the period of their accumulation. We have, however, no means at present of judging of the lapse of time thus indicated except by analogies and comparisons which may be disputed. 6. The human implements which are associated with the remains of extinct Mammals, themselves bear evidence of an exceedingly barbarous condition of the human species. Post- Pliocene or * Palaeolithic” Man was clearly unacquainted with the use of any of the metals. Not only so, but the workman- ship of these ancient races was much inferior to that of the later tribes, who were also ignorant of the metals, and who also used nothing but weapons and tools of stone, bone, &c. 7. Lastly, it is only with the human remains of the Post- Pliocene period that the paleontologist proper has to deal. When we enter the “ Recent” period, in which the remains of Man are associated with those of existing species of Mammals, we pass out of the region of pure palzeontology into the do- main of the Archeologist and the Ethnologist. LITERATURE. The following are some of the principal works and memoirs to which the student may refer for information as to the Post-Pliocene deposits and the remains which they contain, as well as to the primitive races of man- kind :— (1) ‘ Elements of Geology.’ Lyell. (2) ‘ Antiquity of Man.’ Lyell. ) § Palzeontological Memoirs.’ Falconer. (4) ‘The Great Ice-age.” James Geikie. (5) ‘ Manual of Palzontology.’ Owen. (6) * British Fossil Mammals and Birds.’ Owen. (7) ‘Cave-Hunting.’ Boyd Dawkins. (8) ‘ Prehistoric Times.’ Lubbock. (9) ‘ Ancient Stone Implements.’ Evans. (10) ‘ Prehistoric Man.’ Daniel Wilson. (11) ‘Prehistoric Races of the United States.’ Foster. (12) ‘Manual of Geology.’ Dana. HISTORICAL PALZONTOLOGY. ‘Monograph of Pleistocene Mammalia’ (Palzontographical So- ciety). Boyd Dawkins and Sanford. ‘Monograph of the Post-Tertiary Entomostraca of Scotland, &c., with an Introduction on the Post-Tertiary Deposits of Scotland’ (Ibid.). G. S. Brady, H. W. Crosskey, and D. Robertson. ** Reports on Kent’s Cavern” —‘ British Association Reports.’ Pengelly. “Reports on the Victoria Cavern, Settle ’’—‘ British Association Reports.’ Tiddeman. ‘Ossemens Fossiles.’? Cuvier. ‘Reliquize Diluviane.’ Buckland. ** Fossil Mammalia”—‘ Zoology of the Voyage of the Beagle.’ Owen. ‘Description of the Tooth and Part of the Skeleton of the Gly- todon.’ Owen. ** Memoir on the Extinct Sloth Tribe of North: America ”—‘ Smith- sonian Contributions to Knowledge.’ Leidy. ** Report on Extinct Mammals of Australia ’’—‘ British Association,’ 1844. Owen. ‘ Description of the Skeleton of an Extinct Gigantic Sloth (JZylodon robustus).’? Owen. “* Affinities and Probable Habits of Thylacoleo””—‘ Quart. Journ. Geol. Soc.,’ vol. xxiv. Flower. ‘ Prodromus of the Palaeontology of Victoria.’ M ‘Coy. ‘Les Ossemens Fossiles des Cavernes de Liége.’? Schmerling. ‘Die Fauna der Pfahlbauten in der Schweiz.’ Riitimeyer. ** Extinct and Existing Bovine Animals of Scandinavia ’””—‘ Annals of Natural History,’ ser. 2, vol. iv., 1849. Nilsson. ‘Man’s Place in Nature.’ Huxley. ‘Les Temps Antéhistoriques en Belgique.’ Dupont. “Classification of the Pleistocene Strata of Britain and the Conti- nent ”—‘ Quart. Journ. Geol. Soc.,’ vol. xxviii. Boyd Dawkins. * Distribution of the Post - Glacial Mammalia’ (Ibid.), vol. xxv. Boyd Dawkins. ‘On British Fossil Oxen’ (Ibid.), vols. xxii. and xxiii. Boyd Dawkins. ‘British Prehistoric Mammals’ (Congress of Prehistoric Arche- ology, 1868). Boyd Dawkins. ‘ Reliquize Aquitanicz.’ Lartet and Christy. ‘Zoologie et Paléontologie Francaises.’ Gervais. ‘ Notes on the Post-Pliocene Geology of Canada.’ Dawson. **On the Connection between the existing Fauna and Flora ot Great Britain and certain Geological Changes” —‘ Mem. Geol. Survey.’ Edward Forbes. ‘Cavern-Researches.” M‘Enery. Edited by Vivian. ** Quaternary Gravels”—‘ Quart. Journ. Geol. Soc.,’ vol. xxv. Tylor. SUCCESSION OF LIFE UPON THE GLOBE. 367 CHAPTER 22XHE THE SUCCESSION OF LIFE*UPON THE GLOBE. In conclusion, it may not be out of place if we attempt to summarise, in the briefest possible manner, some of the prin- cipal results which may be deduced as to the succession of life upon the earth from the facts which have in the preceding portion of this work been passed in review. ‘That there was a time when the earth was void of life is universally admitted, though it may be that the geological record gives us no direct evidence of this. That the globe of to-day is peopled with innumerable forms of life whose term of existence has been, for the most part, but as it were of yesterday, is likewise an assertion beyond dispute. Can we in any way connect the present with the remote past, and can we indicate even im- perfectly the conditions and laws under which the existing order was brought about? ‘The long series of fossiliferous deposits, with their almost countless organic remains, is the link between what has been and what is; and if any answer to the above question can be arrived at, it will be by the careful and conscientious study of the facts of Palseontology. In the present state of our knowledge, it may be safely said that anything like a dogmatic or positive opinion as to the precise sequence of living forms upon the globe, and still more as to the manner in which this sequence may have been brought about, is incapable of scientific proof. There are, however, certain general deductions from the known facts which may be regarded as certainly established. In the first place, it is certain that there has been a succession of life upon the earth, different specific and generic types suc- ceeding one another in successive periods. It follows from this, that the animals and plants with which we are familiar as living, were not always upon the earth, but that they have been preceded by numerous races more or less differing from them. What is true of the species of animals and plants, is true also of the higher zoological divisions; and it is, in the second place, quite certain that there has been a similar saccession in the order of appearance of the primary groups (‘ sub-king- doms,” “classes,” &c.) of animals and vegetables. These great groups did not all come into existence at once, but they made their appearance successively. It is true that we can- not be said to be certainly acquainted with the first absolute 368 HISTORICAL PALZONTOLOGY. appearance of any great group of animals. No one dare assert positively that the apparent first appearance of Fishes in the Upper Silurian is really their first introduction upon the earth: indeed, there is a strong probability against any such supposition. ‘To whatever extent, however, future discoveries may push back the first advent of any or of all of the great groups of life, there is no likelihood that anything will be found out which will materially alter the ve/ative succession of these groups as at present known to us. It is not likely, for example, that the future has in store for us any discovery by which it would be shown that Fishes were in existence before Molluscs, or that Mammals made their appearance before Fishes. The sub-kingdoms of Invertebrate animals were all represented in Cambrian times—and it might therefore be in- ferred that ¢iese had all come simultaneously into existence; but it is clear that this inference, though incapable of actual disproof, is in the last degree improbable. Anterior to the Cambrian is the great series of the Laurentian, which, owing to the metamorphism to which it has been subjected, has so far yielded but the singular Hozoou. We may be certain, however, that others of the Invertebrate sub-kingdoms besides the Protozoa were in existence in the Laurentian period ; and we may infer from known analogies that they appeared suc- cessively, and not simultaneously. When we come to smaller divisions than the sub-king- doms—such as classes, orders, and families—a similar suc- cession of groups is observable. The different classes of any given sub-kingdom, or the different orders of any given class, do not make their appearance together and all at once, but they are introduced upon the earth in succession. More than this, the different classes of a sub-kingdom, or the differ- ent orders of a class, zz the main succeed one another in the relative order of their zoological rank ing first and the higher groups last. It is true that in the Cambrian formation—the earliest series of sediments in which fossils are abundant—we find numerous groups, some very low, others very high, in the zoological scale, which appear to have simultaneously flashed into existence. For reasons stated above, however, we cannot accept this appearance as real; and we must believe that many of the Cambrian groups of animals really came into being long before the commence- ment of the Cambrian period. At any rate, in the long series of fossiliferous deposits of later date than the Cambrian the above-stated rule holds good as a broad generalisation—that the lower groups, namely, precede the higher in point of time ; SUCCESSION OF LIFE UPON THE GLOBE. 369 and though there are apparent exceptions to the rule, there are none of such a nature as not to admit of explanation. Some of the leading facts upon which this generalisation is founded will be enumerated immediately ; but it will be well, in the first place, to consider briefly what we precisely mean when we speak of ‘‘ higher” and “lower” groups. It is well known that naturalists are in the habit of “ clas- sifying” the innumerable animals which now exist upon the globe; or, in other words, of systematically arranging them into groups. The precise arrangement adopted by one naturalist may differ in minor details from that adopted by another; but all are agreed as to the fundamental points of classification, and all, therefore, agree in placing certain groups in a certain sequence. What, then, is the principle upon which this sequence is based? Why, for example, are the Sponges placed below the Corals; these below the Sea-urchins; and these, again, below the Shell-fish? Without entering into a discussion of the principles of zoological classification, which would here be out of place, it must be sufficient to say that the sequence in question is based upon the relative type of organisation of the groups of animals classified. The Corals are placed above the Sponges upon the ground that, regarded as a whole, the flax or type of structure of a Coral is more complex than that of a Sponge. It is not in the slightest degree that the Sponge is in any respect less highly organised or less perfect, as a Sponge, than is the Coral as a Coral. Each is equally perfect in its own way; but the structural pattern of the Coral is the highest, and therefore it occupies a higher place in the zoological scale. It is upon this principle, then, that the primary subdivisions of the animal kingdom (the so-called ‘sub-kingdoms”) are arranged in a certain order. Coming, again, to the minor subdivisions (classes, orders, &c.) of each sub-kingdom, we find a different but entirely analogous principle employed as a means of classification. ‘The numerous animals belonging to any given sub-kingdom are formed upon the same fundamental plan of structure; but they nevertheless admit of being ar- ranged in a regular series of groups. All the Shell-fish, for example, are built upon a common plan, this plan representing the ideal Mollusc; but there are at the same time various groups of the A7ollusca, and these groups admit of an arrange- ment in a given sequence. ‘The principle adopted in this case is simply of the relative elaboration of the common type. The Oyster is built upon the same ground-plan as the Cuttle-fish; but this plan is carried out with much greater elaboration, and with many more complexities, in the latter than in the former: and 2A 3yVO - HISTORICAL PALAZZAONTOLOGY. in accordance with this, the Cephalopoda constitute a higher group than the Bivalve Shell-fish. As in the case of superiority of structural type, so in this case also, it is not in the least that the Oyster is an zmperfect animal. On the contrary, it is just as perfectly adapted by its organisation to fill its own sphere and to meet the exigencies of its own existence as is the Cuttle-fish ; but the latter lives a life which is, physiologically, higher than the former, and its organisation is correspondingly increased in complexity. This being understood, it may be repeated that, in the main, the succession of life upon the globe in point of time has corresponded with the relative order of succession of the great groups of animals in zoological rank ; and some of the more striking examples of this may be here alluded to. Amongst the £chinoderms, for instance, the two orders gen- erally admitted to be the “lowest” in the zoological scale— namely, the Crzzozds and the Cystotds—are likewise the oldest, both appearing in the Cambrian, the former slowly dying out as we approach the Recent period, and the latter disappearing wholly before the close of the Palzeozoic period. Amongst the Crustaceans, the ancient groups of the Trilobites, Ostracodes, Phyllopods, Eurypterids, and Limuloids, some of which exist at the present day, are all “low” types; whereas the highly- organised Decapods do not make their appearance till near the close of the Palaeozoic epoch, and they do not become abun- dant till we reach Mesozoic times. Amongst the AZollusca, those Bivalves which possess breathing-tubes (the “siphonate Bivalves) are generally admitted to be higher than those which are destitute of these organs (the ‘‘asiphonate” Bivalves) ; and the latter are especially characteristic of the Palzeozoic period, whilst the former abound in Mesozoic and Kainozoic forma- tions. Similarly, the Univalves with breathing-tubes and a corresponding notch in the mouth of the shell (‘siphonosto- matous” Univalves) are regarded as higher in the scale than the round-mouthed vegetable-eating Sea-snails, in which no respiratory siphons exist (‘‘holostomatous” Univalves); but the latter abound in the Palzeozoic rocks—whereas the former do not make their appearance till the Jurassic period, and their higher groups do not seem to have existed till the close of the Cretaceous. The Cephalopods, again—the highest of all the groups of Mollusca—are represented in the Palaeozoic rocks exclusively by Tetrabranchiate forms, which constitute the lowest of the two orders of this class; whereas the more highly specialised Dibranchiates do not make their appearance till the commencement of the Mesozoic. The Palzozoic SUCCESSION OF LIFE UPON THE GLOBE. 371 Tetrabranchiates, also, are of a much simpler type than the highly complex Ammonitide of the Mesozoic. Similar facts are observable amongst the Vertebrate animals. The /ishes are the lowest class of Vertebrates, and they are the first to appear, their first certain occurrence being in the Upper Silurian ; whilst, even if the Lower Silurian and Upper Cambrian ‘‘ Conodonts ” were shown to be the teeth of Fishes, there would still remain the enormously long periods of the Laurentian and Lower Cambrian, during which there were In- vertebrates, but no Vertebrates. The Amphibians, the next class in zoological order, appears later than the Fishes, and is not represented till the Carboniferous; whilst its highest group (that of the Frogs and Toads) does not make its entrance upon the scene till Tertiary times are reached. The class of the /epiiles, again, the next in order, does not appear till the Permian, and therefore not till after Amphibians of very varied forms had been in existence for a protracted period. The Birds seem to be undoubtedly later than the Reptiles ; but, owing to the uncertainty as to the exact point of their first appearance, it cannot be positively asserted that they pre- ceded Mammals, as they should have done. Finally, the Mesozoic types of AJammals are mainly, if not exclusively, referable to the JZarsupzals, one of the lowest orders of the class ; whilst the higher orders of the ‘ Placental ” Quadrupeds are not with certainty known to have existed prior to the com- mencement of the Tertiary period. Facts of a very similar nature are offered by the succession of Plants upon the globe. Thus the vegetation of the Palzo- zoic period consisted principally of the lowly-organised groups of the Cryptogamous or Flowerless plants. The Mesozoic formations, up to the Chalk, are especially characterised by the naked-seeded Flowering plants—the Conifers and the Cycads ; whilst the higher groups of the Angiospermous Exogens and Monocotyledons characterise the Upper Cretaceous and Ter- tiary rocks. Facts of the above nature—and they could be greatly multi- plied—seem to point clearly to the existence of some law of progression, though we certainly are not yet in a position to formulate this law, or to indicate the precise manner in which it has operated. ‘Two considerations, also, must not be over- looked. In the first place, there are various groups, some of them highly organised, which make their appearance at an ex- tremely ancient date, but which continue throughout geological time almost unchanged, and certainly unprogressive. Many of these “ persistent types” are known—such as various of the 372 HISTORICAL PALAZSONTOLOGY. Foraminifera, the Lingule, the Mautili, &c.; and they indicate that under given conditions, at present unknown to us, it is possible for a life-form to subsist for an almost indefinite period without any important modification of its structure. In the second place, whilst the facts above mentioned point to some general law of progression of the great zoological groups, it cannot be asserted that the primeval types. of any given group are necessarily “ lower,’ zooiogically speaking, than their modern representatives. Nor does this seem to be at all necessary for the establishment of the law in question. It cannot be asserted, for example, that the Ganoid and Placoid Fishes of the Upper Silurian are in themselves less highly organised than their existing representatives ; nor can it even be asserted that the Ganoid and Placoid orders are low groups of the class Pisces. On the contrary, they are high groups; but then it must be remembered that these are probably not really the first Fishes, and that if we meet with Fishes at some future time in the Lower Silurian or Cambrian, these may easily prove to be representatives of the lower orders of the class. This question cannot be further entered into here, as its discussion could be carried out to an almost unlimited length; but whilst there are facts pointing both ways, it appears that at present we are not justified in asserting that the earlier types of each group—so far as these are known to us, or really are without predecessors—are zecessarily or invariably more “degraded” or “embryonic” in their structure than their more modern representatives. It remains to consider very briefly how far Paleontology supports the doctrine of ‘‘ Evolution,” as it is called ; and this, too, is a question of almost infinite dimensions, which can but be glanced at here. Does Paleontology teach us that the almost innumerable kinds of animals and plants which we know to have successively flourished upon the earth in past times were produced separately and wholly independently of each other, at successive periods? or does it point to the theory that a large number of these supposed distinct forms have been in reality produced by the slow modification of a comparatively small number of primitive types? Upon the whole, it must be unhesitatingly replied that the evidence of Paleontology is in favour of the view that the succession of life-forms upon the globe has been to a large extent regulated by some orderly and constantly-acting law of modification and evolution. Upon no other theory can we comprehend how the fauna of any given formation is more closely related to that of the formation next below in the series, and to that of ‘SUCCESSION OF LIFE UPON THE GLOBE. 373 the formation next above, than to that of any other series of deposits. Upon no other view can we comprehend why the Post-Tertiary Mammals of South America should consist prin- cipally of Edentates, Llamas, Tapirs, Peccaries, Platyrhine Monkeys, and other forms now characterising this continent ; whilst those of Australia should be wholly referable to the order of Marsupials. On no other view can we explain the common occurrence of “intermediate” or “ transitional ” forms of life, filling in the gaps between groups now widely distinct. On the other hand, there are facts which point clearly to the existence of some law other than that of evolution, and pro- bably of a deeper and more far-reaching character. Upon no theory of evolution can we find a satisfactory explanation for the constant introduction throughout geological time of new forms of life, which do not appear to have been preceded by pre-existent allied types. The Graptolites and Trilobites have no known predecessors, and leave no known successors. The Insects appear suddenly in the Devonian, and the Arachnides and Myriapods in the Carboniferous, under well-differentiated and highly-specialised types. The Dibranchiate Cephalopods appear with equal apparent suddenness in the older Mesozoic deposits, and no known type of the Paleozoic period can be pointed to as a possible ancestor. The A/ippuritide of the Cretaceous burst into a varied life to all appearance almost immediately after their first introduction into existence. The wonderful Dicotyledonous flora of the Upper Cretaceous period similarly surprises us without any prophetic annuncia- tion from the older Jurassic. Many other instances could be given; but enough has been said to show that there is a good deal to be said on both sides, and that the problem is one environed with profound difficul- ties. One point only seems now to be universally conceded, and that is, that the record of life in past time is not interrupted by gaps other than those due to the necessary imperfections of the fossiliferous series, to the fact that many animals are in- capable of preservation in a fossil condition, or to other causes of a like nature. All those who are entitled to speak on this head are agreed that the introduction of new and the destruc- tion of old species have been slow and gradual processes, in no sense of the term “‘catastrophistic.” Most are also willing to admit that ‘‘ Evolution” has taken place in the past, to a greater or less extent, and that a greater or less number of so- called species of fossil animals are really the modified descend- ants of pre-existent forms. ow this process of evolution has 374 HISTORICAL PALAEONTOLOGY. been effected, to what extent it has taken place, under what conditions and laws it has been carried out, and how far it may be regarded as merely auxiliary and supplemental to some deeper law of change and progress, are questions to which, in spite of the brilliant generalisations of Darwin, no satisfactory answer can as yet be given. In the successful solution of this problem—if soluble with the materials available to our hands —will lie the greatest triumph that Paleeontology can hope to attain ; and there is reason to think that, thanks to the guiding- clue afforded by the genius of the author of the ‘ Origin of Species,’ we are at least on the road to a sure, though it may be a far-distant, victory. 375 AL Py BON. alike TABULAR VIEW OF THE CHIEF DIVISIONS OF THE ANIMAL KINGDOM. (Extinct groups are marked with an asterisk. Groups not represented at all as fossils are marked with two asterisks. ) INVERTEBRATE ANIMALS. SUB-KINGDOM I.—PROTOZOA. Animal simple or compound ; body composed of ‘‘sarcode,” not de- finitely segmented ; no nervous system; and no digestive apparatus, beyond occasionally a mouth and gullet. Crass I. GREGARINID/.** Cuiass II. RHIZOPODA. Order 1. Monera.** n 2. Amebea.** n 3. Foraminifera. » 4. Radiolaria (Polycystines, &c.) n 5. Spongida (Sponges). Crass IIT. INrusorra:** SUB-KINGDOM II.—CCELENTERATA. Animal simple or compound ; body-wall composed of two principal layers ; digestive canal freely communicating with the general cavity of the body ; no circulating organs, and no nervous system ora rudimentary one ; mouth surrounded by tentacles, arranged, like the internal organs, in a ‘*radiate”’ or star-like manner. Crass I, Hyprozoa. Sub-class 1. Hydroida (** Hydroid Zoophytes’’). x. Fresh- water Polypes,** Pipe-corallines (Zwudularia), Sea - Firs (Sertularia). Sub-class 2. Siphonophora** (‘Oceanic Hydrozoa”). £x. Portuguese Man-of-war (Physalia). 376 APPENDIX. Sub-class 3. Discophora (‘‘ Jelly-fishes’’). Only known as fossils by impressions of their stranded carcasses. Sub-class 4. Lucernarida (*‘ Sea-blubbers”). Also only known as fossils by impressions left in fine-grained strata. Sub-class 5. Graptolitide * (*‘ Graptolites’’). CuLass II. ACTINOZOA. Order 1. Zoantharia. Ex. Sea-anemones** (Actinide), Star- corals (Astreide). Order 2. Alcyonaria. Ex. Sea-pens (Pennatula), Organ-pipe Coral (7udipfora), Red Coral (Corallium). Order 3. Rugosa (‘* Rugose Corals”’). n .4. Ctlenophora.** LEx. Venus’s Girdle (Cestum). SUB-KINGDOM III.—ANNULOIDA. Animals in which the digestive canal is completely shut off from the cavity of the body; a distinct nervous system; a system of branched ‘* water-vessels,” which usually communicate with the exterior. Body of the adult often ‘‘radiate,”’ and never composed of a succession of definite rings. Cuiass I. ECHINODERMATA. Order 1. Crinoidea (‘‘ Sea-lilies”). 2x. Feather-star (Coma- tula), Stone-lily (Zucrinus*). Order 2. Blastoidea* (*‘ Pentremites’’). n 3. Cystotdea* (‘* Globe-lilies’’). n 4. Ophiuroidea (‘‘ Brittle-stars”). x. Sand-stars (Ophz- ura), Brittle-stars (Ofhzocoma). Order 5. Asteroidea (*‘ Star-fishes”’). £x. Cross-fish (Uvaster), Sun-star (.So/aster). Order 6. Echinoidea (‘‘Sea-urchins”). Lx. Sea-eggs (Echinus), Heart-urchins (Spatangus). Order 7. Holothuroidea (‘‘Sea-cucumbers”). x. Trepangs (Holothuria). Cuiass II. SCOLEcIDA ** (Intestinal Worms, Wheel Animalcules, &c.) SuUB-KINGDOM IV.—ANNULOSA. Animal composed of numerous definite segments placed one behind the other ; nervous system forming a knotted cord placed along the lower (ventral) surface of the body. Division A. Anarthropoda. No jointed limbs. Crass I, GEPHYREA** (‘‘Spoon-worms”’). CuLass II, ANNELIDA (‘‘ Ringed-worms”). £2. Leeches** (Hirudinea), Earthworms** (Oligocheta), Tube-worms (7zdicola), Sea - worms and Sea-centipedes (Zrraztia). Cuiass III. CH2ZTOGNATHA** (‘‘ Arrow-worms”’), Division B. Arthropoda or Articulata. Limbs jointed to the body. Crass I. CRusTACEA (‘‘ Crustaceans’’), 4x. Bamacles and Acorn- shells (Civripedia), Water- fleas (Ostracoda), Brine -shrimps and Fairy-shrimps (Phyllofoda), Trilobites * (Z7ilodita), King - crabs and Eurypterids* (JZerostomata), Wood-lice and Slaters (/sofoda), Sand-hoppers (Amphipoda), Lobsters, Shrimps, Hermit-crabs, and Crabs (Decapoda). APPENDIX. 397 Cxiass II. ARACHNIDA. Lx. Mites (Acarina), Scorpions (Pedipalpi), Spiders (Avaneida). Cuass III. Myritapopa. x. Centipedes (Chzlopoda), Millipedes and Galley-worms (Chilognatha). Cxiass IV. Insecra (*‘ Insects”). 2x. Field-bugs (Hemiptera) ; Crick- ets, Grasshoppers, &c. (Orthoptera); Dragon-flies and May-flies (Neuroptera) ; Gnats and House-flies (Diptera); Butterflies and Moths (Lepidoptera); Bees, Wasps, and Ants (“ymenoptera) ; Beetles (Coleoptera). SUB-KINGDOM V.—MOLLUSCA. Animal soft-bodied, generally with a hard covering or shell ; no dis- tinct segmentation of the body; nervous system of scattered masses. Cuass I. Potyzoa (‘‘Sea-Mosses”). x. Sea-mats (/lustra), Lace- corals (Fenestellide*). Cuass II. TunicaTa** (‘‘ Tunicaries”). Zx. Sea-squirts (Ascidia). Cuiass IIIf. BRAcHIOPODA (‘‘Lamp-shells”’). £%. Goose-bill Lamp- shell (Zizguda). Ciass IV. LAMELLIBRANCHIATA (‘‘ Bivalves”). x. Oyster (Ostrea), Mussel (AZytilus), Scallop (Pecten), Cockle (Cardiunz). CLAss V. GASTEROPODA (‘‘ Univalves”). Zax. Whelks (Buccinume), Limpets (Pavel/a), Sea-slugs** (Doris), Land-snails (/e/ix). CLaAss VI. PTEROPODA (‘‘ Winged Snails”). Ex. Wyalea, Cleodora. CiLass VII. CEPHALOPODA (‘*‘ Cuttle-fishes ”). 2x. Calamary (ZLodzgo), Poulpe (Octopus), Paper Nautilus (Avgonauta), Pearly Nautilus (Nautilus), Belemnites,* Orthoceratites,* Ammonites.* VERTEBRATE ANIMALS. SUB-KINGDOM VI.—VERTEBRATA. Body composed of definite segments arranged longitudinally one behind the other; main masses of the nervous system placed dorsally; a back- bone or ‘‘ vertebral column” in the majority. Ciass I. Pisces (‘‘ Fishes”). x. Lancelet** (Amfhioxus) ; Lampreys and Hag-fishes (Marsipobranchii**); Herring, Salmon, Perch, &c. (Zeleostei or *‘ Bony Fishes”); Gar-pike, Sturgeon, &c. (Ganordet) ; Sharks, Dog-fishes, Rays, &c. (Zvasmobranchit or ‘ Placoids”). Ciass I]. AMpHrBIA (‘f Amphibians”). Ex. Ladbyrinthodontia,* Cx- cilians,** Newts and Salamanders (Uvodea), Frogs and Toads (Anoura). Ciass III. REepTILiA (‘‘ Reptiles”). Ex. Deinosauria,* Pterosauria,* Anomodontia,* Plesiosaurs (Sauropterygia*), Ichthyosaurs (Zch/hy- opterygia*), Tortoises and Turtles (Chelonia), Snakes (Ofhidia), Lizards (Lacertilia), Crocodiles (Crocodilia). Ciass IV. Aves (“Birds”). 2x. Toothed Birds (Odontornithes*) ; Lizard-tailed Birds (Archeopteryx*); Ducks, Geese, Gulls, &c. (Natatores) ; Storks, Herons, Snipes, Plovers, &c. (Gradlatores) ; Ostrich, Emeu, Cassowary, Dinornis,* /£piornis,* &c. (Czrsores) ; Fowls, Game Birds, and Doves (Rasores) ; Cuckoos, Woodpeckers, Parrots, &c. (Scansores); Crows, Starlings, Finches, Humming- birds, Swallows, &c. (Zusessores) ; Owls, Hawks, Eagles, Vultures (Raptores). 378 APPENDIX. CLaAss V. MAMMALIA (‘‘ Quadrupeds”’). £x. Duck-mole and Spiny Ant-eater (J/onotremata**); Kangaroos, Phalangers, Opossums, Tasmanian Devil, &c. (AZarsupialia) ; Sloths, Ant-eaters, Arma- dillos (Edentata); Manatees and Dugongs (Szvenia); Whales, Dolphins, Porpoises (Cefacea) ; Rhinoceros, Tapir, Horses, Hip- popotamus, Pigs, Camels and Llamas, Giraffes, Deer, Antelopes, Sheep, Goats, Oxen (Ungulata); Hyrax (Hyracoidea**); Ele- phants, Mastodon,* Deinotherium®* (Prodoscidea) ; Seals, Walrus, Bears, Dogs, Wolves, Cats, Lions, Tigers, &c. (Carnivora) ; Hares, Rabbits, Porcupines, Beavers, Rats, Mice, Lemmings, Squirrels, Marmots, &c. (Rodentia); Bats (Cheiroptera) ; Moles, Shrew-mice, Hedgehogs (/rsectivora) ; Lemurs, Spider-monkeys, Macaques, Baboons, Apes (Quadrumana) ; Man (Bimana). 379 GES Sa. ie ABDOMEN (Lat. abdo, I conceal), The posterior cavity of the body, contain- ing the intestines and others of the viscera. In many Invertebrates there is no separation of the body-cavity into thorax and abdomen, and it is only in the higher Annulosa that a distinct abdomen can be said to exist. ABERRANT (Lat. aberro, I wander away). Departing from the regular type. ABNORMAL (Lat. ab, from; norma, a rule), Irregular; deviating from the ordinary standard. Acrovus (Gr. akros, high ; odous, tooth). A genus of the Cestraciont fishes. so called from the elevated teeth. AcrocEns (Gr. akros, high; gennao, I produce). Plants which increase in height by additions made to the summit of the stem by the union of the bases of the leaves. AcroTReETA (Gr. akros, high; trétos, pierced). A genus of Brachiopods, so called from the presence of a foramen at the summit of the shell. ACTINOCRINUS (Gr. aktin, aray; krinon, a lily). A genus of Crinoids. Actinozoa (Gr. aktin, a ray; and zoén, an animal). That division of the Celenterata of which the Sea-anemones may be taken as the type. ARGLINA (4g/é, a sea-nymph). A genus of Trilobites. JEPIORNIS (Gr. aipus, huge; ornis, bird). Phillipsia, 179 ; seminifera, 180. Pholadomya, 235. Phormosoma, 178. Phorus, 271. Phosphate of lime, concretions of, 30; disseminated in rocks, 30; origin of, 81. Phyllograptus, 102; typus, 102. Phyllopoda, of the Cambrian, 83; of the Lower Silurian, 108; of the Upper Silu- rian, 123; of the Devonian, 145; of the Carboniferous, 179; of the Permian, 197 ; of the Trias, 210. INDEX. Phyllopora, 210. Physa, 294 ; columnaris, 294. Pigs, 302, 317, 329, 354. Pilton Group, 135. Pinites, 170. Pisces (see Fishes). Pisolite, 29. Pisolitic Limestone of France, 259, 286. Placodus, 220 ; gigas, 220. Placoid Fishes, 150; of the Upper Silurian, 130, 131; of the Devonian, 153-155; of the Carboniferous, 188; of the Permian, 199; of the Trias, 214; of the Jurassic, 241; of the Cretaceous, 275; of the Eocene, 295; of the Miocene, 312. : Plagiaulax, 254. Planolites, 122; vulgaris, 123. Planorbis, 294. Plants, of the Cambrian, 80, 81; of the Lower Silurian, 97, 98; of the Upper Silurian, 118; of the Devonian, 136-139 ; of the Carboniferous, 163-170; of the Permian, 196; of the Trias, 207, 208 ; of the Jurassic, 229, 230; of the Cre- taceous, 261-263; of the Eocene, 289, 290; of the Miocene, 308-311. Plasmopora, 119. Platanus, 262, 308 ; aceroides, 309. Platephemera antiqua, 145. Platyceras, 128, 148; dumosum, 148; multisinuatum, 129; ventricosum, 129. Platycrinus, 122, 175; tricontadactylus, 175. Platyostoma, 129; Niagarense, 129. Platyrhine Monkeys, 362. Platyschisma helicites, 129. Platysomus, 200; gibbosus, 199. Platystoma, 213. Pleistocene period, 334; climate of, 362. Plesiosaurus, 219, 243-245, 276; dolicho- deirus, 244. Pleurocystites squamosus, 106. Pleurotoma, 293. Pleurotomaria, 111, 129, 186, 199, 236, 271. Plicatula, 213. Pliocene period, 323; rocks of, in Britain, 324; in Belgium, 325; in Italy, 325; in North America, 326; life of, 326-331. Pliopithecus, 322; antiquus, 323. Pliosaurus, 245. Podoecarya, 230. Podozamites, 208; lanceolatus, 209. Polir-schiefer, 33. Polycystina, 32; of Barbadoes-earth, 33. Polypora, 145, 184; dendroides, 183. Polypterus, 153, 188. Polystomella, 311. Polytremacis, 266. Polyzoa, of the Cambrian, 81, 89; of the Lower Silurian, 108; of the Upper Silurian, 125; of the Devonian, 145, 146; of the Carboniferous, 183, 184; of the Permian, 198; of the Trias, 210; of the Cretaceous, 267 ; of the Miocene, 312. Populus, 262. Porcellia, 186. Porcupines, 322. Portage Group, 135. Port-Jackson Shark, 154, 188, 242. Portland beds, 227, 229. Post-Glacial deposits, 336, 338. INDEX. Post-Pliocene period, 334. Post-Tertiary period, 286. Poteriocrinus, 175. Potsdam Sandstone, 79. Pre-Glacial deposits, 336. Prestwichia, 179; rotundata, 179. Primitia, 107; strangulata, 107. Primordial Trilobites, 85. Primordial zone, 79. Proboscidea, of the Miocene, 319, 322; of the Pliocene, 329, 330; of the Post- Pliocene, 357-359. Producta, 147, 184, 198; horrida, 1983 longispina, 185; semireticulata, 185. Productella, 147, 184. Productide, 147, 211. Proeétus, 123. Prong-buck, 318. Protaster, 120; Sedqwickii, 121. Proteacee, 262, 308, 309. Proteus, 189. Protichnites, 87. Protocystites, 82. Protormis Glarisiensis, 297. Protorosaurus, 201, 202; Speneri, 201. Protospongia, 81; jfenestrata, 88. Prototax#tes, 118, 1388; Logani, 139. Psammobia, 292. Psammodus, 188. Psaronius, 136, 164. Pseudocrinus bifasciatus, 106. Psilophyton, 118, 137, 138; princeps, 138. Pteranodon, 247, 277; longiceps, 277. Pteraspis, 130, 152; Banksti, 1380. Pterichthys, 152; cornutus, 153. Pterinea, 128; subfaleata, 128. Pteroceras, 237, 271. Pterodactylus, 245, 277; crassirostris, 246 Pterophyllum, 208, 230; Jaegeri, 209. Pteropoda, of the Cambrian, 88; of the Lower Silurian, 111; of the Upper Silurian, 129; of the Devonian, 148; of the Carboniferous, 186; of the Per mian, 199; of the Jurassic, 237. Pterosauria, 245; of the Jurassic, 245-248; of the Cretaceous, 277. Pterygotus Anglicus, 124, 125. Ptilodictya, 108, 125; acuta, 109; falci- Formis, 109; raripora, 126; Schaffer, 109. Ptychoceras, 273; Emericianum, 274. Ptychodus, 275. Pupa vetusta, 186. Purbeck Beds, 228; Mammals of, 254. Purpuroidea, 237. Pycnodus, 275. Pyrula, 293. Quadrumana, of the Eocene, 305; of the Miocene, 322, 323; of the Pliocene, 331; of the Post-Pliocene, 361. Quadrupeds (see Mammalia). Quaternary period, 334. Quebec Group, 95, 96, 101. Quercus, 262. . Rabbits, 322. ~ Rana, 313. Raptores, 297. Rasores, 297. Recent period, 286, 334. Receptaculites, 99. 405 Red clays, origin of, 35. Red Coral, 311. Red Crag, 324. Red Deer, 336, 354. Reindeer, 344, 345, 354, 355. Remopleurides, 188. Reptiles, 200; of the Permian, 200-202; of the Trias, 217-221; of the Jurassic, 242-251; of the Cretaceous, 276-281; of the Eocene, 296, 297. Retepora, 108, 125, 145, 184, 198, 210; Ehrenbergi, 198; Phillipsi, 146. Retiolites, 119. Retzia, 127. Rhetic Beds, 204-206. Rhamphorhynehus, 247; Bucklandi, 248. Rhinoceride, 315. Rhinoceros Etruscus, 327, 328, 336, 353 ; leptorhinus, 328; megarhinus, 327-329, 336, 353; tichorhinus, 353, 354. Rhinopora verrucosa, 126. Rhizodus, 188. Rhombus minimus, 295. Rhyncholites, 239. Rhynchonella, 110, 127, 147, 184, 234, 268, 292; cuneata, 127; neglecta, 127; pleu- rodon, 185; varians, 235. Rhynchosaurus, 218; articeps, 218. Rice-shells, 293. Richmond Earth, 33, 307. Ringed Worms (see Annelida). River-gravels, high-level and low-level, 340, 341. Robulina, 311. Rocks, definition of, 14; divisions of, 14, 15; igneous, 14; aqueous, 15-18; mechanically-formed, 18-20; chemically- formed, 20; organically-formed, 20-37; arenaceous, 20; argillaceous, 20; cal- careous, 20-32; siliceous, 20, 32-34. Rodentia, of the Eocene, 305; of the Miocene, 322; of the Post-Pliocene, 561. Roebuck, 336, 354. Rostellaria, 237, 293. Rotalia, 22, 98, 171, 264; Boueana, 264. Rugose Corals, 104; of the Lower Silurian, 104, 105; of the Upper Silurian, 119; of the Devonian, 141; of the Carbon- iferous, 172-174; of the Permian, 197; of the Upper Greensand, 266. Rupelian Clay, 307. Sabal major, 309. Sabre-toothed Tiger, 322, 331. Saccammina, 172. Saccosoma, 232. Salamanders, 189, 313. Salina Group, 117. Salix, 262; Meeki, 263. Salmonidce, 276. Sao hirsuta, 85. Sassafras cretacea, 263. Sauropterygia, 219. Scalaria, 271, 293; Grenlandica, 338. Scaphites, 272, 273; @qualis, 274. Schizodus, 198, 211. Schoharie Grit, 135, 137 Scolecoderma, 82. Scoliostoma, 213. Scolithus, 82; Canadensis, 83. Scorpions of the Coal-measures, 181. Scorpion-shells, 271. 406 Screw-pines, 230. Scutella, 311; subrotunda, 312. Sea-cows (see Sirenia). Sea-lilies (see Crinoidea). Sea-lizards (see Enaliosaurians). Seals, 322. Sea-mats and Sea-mosses (see Polyzoa). Sea-shrubs (see Gorgonidz). Sea-urchins (see Echinoidea). Sea-weeds, 80, 81, 83, 97, 136, 164, 261. Secondary period, 44 Sedimentary rocks, 15. Senvnopithecus, 322, 331. Septaria, 31. Sequoia, 306, 309, 310; Couttsicw, 309; gigantea, 309; Langsdorfir, 309. Serolis, 84. Serpents (see Ophidia). Serpulites, 123. Sewalik Hills (see Siwalik Hills). Sheep, 355. Shell-sands, 19. Sigillaria, 168, 169; Greeseri, 168. Sigillarioids, 136, 168, 170, 196. Silicates, infiltration of the shells of For- aminifera by, 34, 74. Siliceous rocks, 20, 32. Siliceous Sponges, 265. Silicification, 13, 14. Silurian period (see Lower Silurian and Upper Silurian), 90-114, 115-132. Simosaurus, 219; Gaillardoti, 219. Siphonia, 264 ; jficus, 265. Siphonostomatous Univalves, 237, 271, 293. Siphonotreta, 110. Surenia, 299, 320; of the Eocene, 299; of the Miocene, 315. Siren lacertina, 200. Sivatherium, 318; gigantewm, 319. Siwalik Hills, Miocene strata of, 307. Skiddaw Slates, 101. Sloths, 315, 349-351. Smilax, 308. Smithia, 173. Snakes (see Ophidia). Soft Tortoises, 296. Solarium, 271. Solenhofen Slates, 228. Solitaire, 346, 348. Spalacotherium, 254. Spatangus, 311. Spherospongia, 139. Sphagodus, 130. Sphenodon, 218. Sphenopteris, 136, 165, 196. Spiders of the Coal-measures, 181. Spider-shells, 237. Spindle-shells, 237. Sptrifera, 125, 147, 184, 198, 284; ecrispa, 127; disjuncta, 147; hysterica, 126; mucronata, 147; Niagarensis, 127; ros- trata, 235; sculptilis,147 ; trigonalis,185. Spiriferide, 147. Spirophyton cauda-Galli, 135, 164. Spirorbis, 123, 148, 178; Arkonensis, 144 ; Carbonarius, 178; laxus, 144; Lewisii, 123 ; omphalodes, 144 ; spinulifera, 144. Spirulirostra, 312. Spondylus, 269; spinosus, 270. Sponges, of the Cambrian, 81; of the Lower Silurian, 98; of the Upper Silu- rian, 119; of the Devonian, 139; of the INDEX. Carboniferous, 171; of the Permian, 197; of the Trias, 209; of the Jurassic, 230; of the Cretaceous, 264, 265. Spongilla, 197. Spongillopsis, 197. Spongophyllum, 173. Spore-cases, of Cryptogams in the Ludlow rocks, 118 ; in the Coal, 163. Squirrels, 322. Stagonolepis, 218. Staircase-shells, 271. Stalactite, 21. Stalagmite, 21. Star-corals, 231. Star-fishes, 105, 120, 210. St Cassian Beds, 205, 206. Stephanophyllia, 266. Stereognathus, 253, 254. Stigmaria, 169; ficoides, 169. Stonesfield Slate, 227; Mammals of, 253. Strata, contemporaneity of, 44. Stratified rocks, 15-18. _ Streptelasma, 105. Streptorhynchus, 198. Stromatopora, 98, 99, 118, 139 ; rugosa, 99; tuberculata, 140. Strombodes, 119; pentagonus, @04. Strombus, 271. Strophalosia, 198. Strophodus, 255. Strophomena, 109, 110, 125, 147, 184; alternata, 110; deltoidea, 109 ; jilitexta, 110; rhomboidalis, 147, 148; subplana, ye Sub-Apennine Beds, 325. Sub-Carboniferous rocks, 158, 161. Succession of life upon the globe, 367-374. Suida, 302, 317, 329. Sulphate of lime, 22. Sus Erymanthius, 317; serofa, 354. Synastrea, 209. Synhelia Sharpeana, 266. Synocladia, 198; virgulacea, 198. Syringopora, 119, 173 ; ramulosa, 174. Tabulate Corals, 104; of the Lower Silu- rian, 105; of the Upper Silurian, 119; of the Devonian, 142; of the Carbon- iferous, 172; of the Permian, 197. Talpa Europea, 336. Tapiride, 300. Tapirs, 300. Tapirus Arvernensis, 327. Taxocrinus tubercuiatus, 122. Taxodium, 262, 308, 31. Teleosaurus, 251. Teleostean Fishes, 150; of the Cretaceous, 276. Telerpeton Elginense, 218. Tellina proxvma, 338 Tentaculites, 129, 148 ; ornatus, 129. Terebra, 293. Terebratella, 268 ; Astieriana, 268. Terebratula, 184, 234 ; digona, 235; elon- gata, 168; hastata, 185; quadrijida, 235 ; spheroidalis, 235. Terebratulina, 268 ; caput-serpentis, 268 ; striata, 268, Termites, 311. Terrapins, 280, 296. Tertiary period, 44, 284-287. Tertiary rocks, classification. of, 284-287 INDEX. Testudinide, 3138. Tetrabranchiate Cephalopods, 112; of the Cambrian, 89; of the Lower Silurian, 112-114 ; of the Upper Silurian, 130; of the Devonian, 149; of the Carboniferous, 186, 187; of the Permian, 199; of the Trias, 212; of the Jurassic, 237-229; of the Cretaceous, 272-274 ; of the Eocene, 294; of the Miocene, 312. Textularia, 22, 264, 311 ; Meyeriana, 311. Thanet Sands, 287, 288. Theca, 88, 111, 129. Theca Davidii, 88. Thecidium, 213. Thecodont Reptiles, 218. Thecodontosaurus, 200, 218; antiquus, 219. Thecosmiha annularis, 231. Thelodus, 131. Theriodont Reptiles, 202, 220. Thylacoleo, 349. Tile-stones, 116. Titanotherium, 316 Toothed Birds, 281-283. Tortoises, 202, 296. Tragoceras, 318. Travertine, 21. Tree-Ferns, of the Devonian, 136; of the Coal-measures, 164. . Tremadoce Slates, 77-79. Trematis, 110. Trenton Limestone, 95, 96. Trianthrus Beckvi, 107. Triassic period, 203; rocks of, in Britain, 204; in Germany, 204; in the Austrian Alps, 205; in North America, 205; life of, 206-224. Triconodon, 254. Trigonia, 235, 255, 269. Trigoniadee, 198, 211. Trigonocarpum, 170 ; ovatum, 170. Trilobites, 84-87; of the Cambrian, 85, 87; of the Lower Silurian, 107, 108; of the Upper Silurian, 123, 124; of the De- vonian, 144, 145; of the Carboniferous, 179. Trimerellide, 127. Trinucleus, 108 ; concentricus, 107. Trionycide, 296. Triton, 293. Trochocyathus, 266. Trochonema, 129. Trogontherium, 361; Cuvieri, 336, 361. Trumpet-shells, 293. Tulip-tree, 262, 308. Turbinolia suleata, 292. Turbinolide, 292. Turrilites, 272, 273; catenulatus, 274. Turritella, 271, 293 Turtles, 202, 251, 280, 296. Typhis tubifer, 293. Ulimania selaginoides, 197. Unconformability of strata, 48. Under-clay of coal, 162. Ungulata, of the Eocene, 300-303 ; of the Miocene, 315-319; of the Pliocene, 327- 329; of the Post-Pliocene, 353-357. Uniformity, doctrine of, 5-7. Unio, 250. 407 Univalves (see Gasteropoda). Upper Cambrian, 77-79; Chalk, 259; Cretaceous, 257, 260; Devonian, 135; Eocene, 287, 288; Greensand, 258; Helderberg, 135 ; Laurentian, 66 ; Llan- dovery, 115; Ludlow rock, 116; Mio- cene, 305; Oolites, 227 : Silurian period, 115; rocks of, in Britain, 115, 116; in North America, 116-118 ; life of, 118-131. Ursus arctos, 359; Arvernensis, 330 ; fe- rox, 359; spelea, 360. Urus, 336, 356. Valley-gravels, high-level and low-level, 339-341. Vanessa Pluto, 312. Varanide, 202. Vegetation (see Plants). Ventriculites, 264, 265 ; simplex, 265. Venus’s Flower-basket, 265. Vermilia, 197. Vespertilio Parisiensis, 304, 305. Vicksburg Beds, 289. Vines, 306, 309, 310. Vitreous Sponges, 264. Voltzia, 208; heterophylla, 209. Voluta, 271, 293 ; elongata, 271. Volutes, 271, 293, 312. Walchia, 196, 197 ; piniformis, 196. Walrus, 322. Wealden Beds, 257. Wellingtona, 309, 310. Wenlock Beds, 115, 117; Limestone, 115; Shale, 115. Wentle-traps, 271. Werfen Beds, 205, 296. Whalebone Whales, 299, 315. Whales, 299, 315. Whelks, 237. White Chalk, 259; structure of, 21, 22; origin of, 23, 263 White Crag, 324. White River Beds, 307. Wild Boar, 354. Williamsonia, 230. Winged Lizards (see Pterosauria). Winged Snails (see Pteropoda). Wing-shells, 271. Wolf, 336, 360. Wolverine, 360. Wombats, 348. Woolhope Limestone, 115. Woolly Rhinoceros, 339, 341, 344, 353. Woolwich and Reading Beds, 287. Worm-burrows, 82, 83, 123. Xanthidia, 138, 161. Xenoneura antiquorum, 145. Xiphodon, 303. Xylobwus, 182; Sigillarice, 182. Zamia spiralis, 208. Zamites, 208, 230, 310. Zaphrentis, 105, 119, 142,173; cornicula, 141; Stokesi, 104; vermicularis, 174. Zeacrinus, 175. Zechstein, 194. Zeuglodon, 299, 315; cetoides, 299, 300 a cA a j Peay sey va) anp.a A ome 5 ’ v4 s - j "ee " i, v. & | os 1 ‘ c te ae oe > de Mg >: My ie , Pm Wh aie égayeh iJ Un f a) . ; “ | ead ee ig mk i. > ; we: i .4fe ii Li ‘lagl a. t i ij ' i} sh ane j ‘ wi wid kd é NS = by s PRINTED BY WILLIAM BLACKWOOD AND SONS. _ ld 4 ’ = . 4 7 ‘ Fj hé i 7 Vv a 1<@s" “A t re Wy 4 é w 7 94 bd wie @ Z Po arn | 4.ats44 v . ss 1} » e-°6 oe | Al e +... | a 2. { a ' a A td SO” at yee oi wi bedu ier Gel Walley, iy VR atl er att a wi od r . , witeles en, ene *7) FAT , Pe fee ives o of is in NE Ee ONS. OF WORKS ON GEOLOGY AND PHYSICAL GEOGRAPHY. By DAVID! PAGE, liga. -ac: Professor of Geology in the Durham University College of Physical Science, Newcastle. Sixth Edition, Revised and Enlarged. ADVANCED TEXT-BOOK OF GEOLOGY. -In crown 8vo,; pp. 536, 7s. 6d. With 153 Engravings, and a Glossary of Scientific Terms. Tenth Edition. INTRODUCTORY “TEXT -BOOK:- OF * GEOLOGY. )-WihiEn- gravings on Wood, and Glossarial Index. Crown 8vo, 2s. 6d. Seventh Edition. THE GEOLOGICAL EXAMINATOR. A Progressive Series of Questions, adapted to the Introductory and Advanced Text-Books of Geology. Prepared to assist Teachers in framing their Examinations, and Students in testing their own Progress and Proficiency. 9d. Sixth Edition. THESCRUST OF THE, EARTH..A. Hanpy OUTLINE OF (GEo- LOGY." Is, Third Edition, Enlarged. GEOLOGY FOR GENERAL READERS. ). Tee ht ay Eee diy iy uy a :y pe INN NUNN 3 2044 107 100 Date Due SAW-a-o-1872 Sah UR ant Nett GI oa Rtn Be sens herb bine SS ae ae fe * : vr ¢ ~ : a ar é . = % . Fi as ete Ee EY LR Naren Tea a EAE Det SL RE PNG iin, Wael ee dee, Po est cat ntact tats nda te ninheitarantsatlicnendinndtiy Sait : EIT Kee ae Tee . ee = Soe . r ~ — he 4 » Ss Treaties . in § ™ * , SA : ¢ : . . ae Re nn = Meso mace Sones anton eae a SLES. a tes an ; may me TS MONS eng CP GE ROA arn = RAO pM rs ae : Sa aoe arena SECS ase eee Date eR te = om . 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