356 



NATURE 



{Aug. 26, 1875 



Justice to say that, single-handed, no such exact map for any 

 one area was ever before constructed, either as regards scale or 

 details. This undertaking occupied its author 15 years, fills 19 

 separate folio maps, and is a most valuable acquisition to the 

 estate-agent, mineral engineer, and practical geologist. Its real 

 merits can only be fully appreciated by those who understand 

 how much patient labour, long-sustained energy, and high 

 mental qualities were required to complete so extended a survey 

 over such a complicated piece of country. In doing this, how- 

 ever, Mr. Sanders has made his scientific reputation, enriched 

 his native country, and achieved a success which falls to the lot 

 of few men. Having considered the stratigraphical relation of 

 the rocks in the Bristol district, I desire now to say a few woids 

 on a branch of the subject which falls more immediately within 

 the range of my own special studies — I mean the organic remains 

 found imbedded in these strata. The science of Paleontology 

 {palnios, old ; onta^ beings) forms an immense field of observa- 

 tion, and one that widens more and more every year. It is 

 impossible to enter upon any of its details now ; but some of 

 its principles may be satisfactorily explained, and this I shall 

 endeavour to do. 



It is now established, ist, that the stratified rocks containing 

 organic remains admit of a division into four great groups, 

 representing four great periods of time : — a, the Palaeozoic or 

 Ancient ; h, the Mesozoic or Middle ; c, the Cainozoic or Ter- 

 tiary ; and d, the Quaternary or Modern periods. 2nd. That 

 each period is distinguished by its own hieroglyphic characters, 

 which are graven on the rocks in definite and determinable 

 characters. 3rd. That these hieroglyphics are the fossil remains 

 or imprints of animals that lived in the water in which the 

 sediments were formed in successive layers on the earth's crust, 

 and are only found in the rocks they distinguish, so that it is 

 possible to determine the age and position of the strata from 

 which they have been collected, or, in other words, identify 

 strata by organic remains ; and by this key we are enabled to 

 read the pages of the Rock-book, study the history of extinct 

 forms of life, and determine their distribution in time and 

 space. 



Let us apply these principles to the subject we have in hand. 

 The Palaeozoic period comprises the history of the Cambro- 

 Silurian, Devonian, Carboniferous, and Permian ages ; and if 

 we attentively examine the fossils of this period, contained in 

 the cases of the magnificent Geological Museum of this institu- 

 tion, we shall see that all the organisms belonging to one age are 

 entirely distinct from those belonging to the others. You will 

 find, for example, in the case of the Silurian age, some beautiful 

 corals, crinoids, and cephalopods, with a remarkable assemblage 

 of Crustacea, the representatives of an extinct family, the Trilo- 

 bitidffi, which are so highly characteristic of this age that the 

 rocks may be called Trilobitic. 



The Devonian age succeeds the Silurian ; and among the corals 

 and shells so well seen in this collection, we observe a striking 

 resemblance to those of the Silurian on the one side and the 

 Carboniferous Limestone on the other ; but when closely ex- 

 amined we find that many are generically, and all are specifically 

 distinct from both ; besides this we discover that a new group of 

 organisms of a different and higher type of stracture are now 

 introduced for the first time, namely, those remarkable forms of 

 tire ichthyic class the fishes of the Old Red Sandstone, and 

 whose singular forms with their bony armour and osseous scales 

 remind us of the remarkable fishes Lepidosteus and Folyptcrus, 

 from North American, African, and Australian rivers of our 

 time. The hieroglyphics, therefore, engraven on the strata of 

 the second age are visibly different from those on the first. 



The Carboniferous succeeds the Devonian ; and here we find 

 a marvellous development of the life of this age preserved in the 

 cases of this institution. Pray study attentively the fine specimens 

 of Anthozoa here exhibited, all derived from the upper beds of 

 the^ Carboniferous Limestone at the gorge of the Avon, and 

 showing very clearly that this portion of the section was formed 

 in a tropical sea, and that the limestone is the product of the 

 living energies of those Polyps, sections of whose skeletons lie 

 there before you. Of the family Favositid^ we see Favosites, 

 Alveolites, Syringopora Michelinia ; and of the family CVATHO- 

 PHYLLiD^ we have Cyathophyllum, Lithostrotion, Lonsdalia, 

 &.C. Many of the beds of limestone are almost entirely composed 

 of the ossicula of Crinoids; and we see the stems, arms, and calyces 

 of these sea-lilies strewed in abundance in the rocks, such as 

 Actinocrinus,Poteriocrinus, Platyctinus, Cyathocrinus, Fentremites, 

 &c., with the remarkable ancient Sea-urchin Falcech'mus asso- 

 ciated with them. The MoUusca were chiefly represented by 



the Bradhiopoda, which were very common in the Carboniferous 

 age, as you may see in the large slabs containing Orthis, 

 Spiri/era, and Froductus in great profusion. The Lamellibran- 

 chiata were represented by Cardiomorpha and Conocardiwn, 

 and the Gasteropoda by Euoinphahis, Fleurotomaria, and Natica, 

 and the Cephalopoda by Goniaiites, Orthoccras, &c. The 

 Trilobites which formed so remarkable a feature in the fauna 

 of the Silurian sea are here represented by a few specimens of 

 Fhillipsia, a dwarfed genus of this family. The fine collection 

 of teeth and spines of large fishes from the Carboniferous Lime- 

 stone enables us to compare the forms of this age with those of 

 the Devonian already desciibed, and shows at a glance that the 

 ichthyic types in the seas of these two periods were entirely 

 distinct, and both evidently adapted to conditions of existence 

 widely different. 



The life of the Carboniferous Limestone proves that it was a 

 great marine formation accumulated during a long lapse of time 

 out of the exuviae and sediments of many generations of Mollusca, 

 Echinodermata, and Actinozoa, the reef-building corals having 

 contributed largely to the thickness of the Coral beds, and the 

 wasted reefs ot former generations having been used up again 

 and again in the formation of the Oolitic beds which succeeded 

 the reef-building periods. 



The Coal Measures present a remarkable contrast to the Coral 

 sea of the Carboniferous era. The Ferns (Sigillaria, Lepido- 

 dendra) and other arborescent Acrogens of the Coal-seams grew 

 and flourished in low islands ; and their remains were accumu- 

 lated under conditions very different from those in which the 

 thick-bedded limestones of the Avon section were formed. Good 

 typical examples of the vegetation of this remarkable tmre in 

 the world's history are well preserved in the large collection, 

 filling several cases ; these specimens are all very fine, and 

 require, and I am sure will have, a careful examination. 



With the close of Palaeozoic time there appears to have been a 

 great break in stratigraphical sequence of the fossiliferous rocks ; 

 mighty changes then took place. Volcanic agency was intense 

 and active, flexing, contorting, and upheaving the older beds. 

 These displacements in our area were post-carboniferous and pre- 

 triassic, and are well exemplified in the unconformable position 

 of the Dolomitic Conglomerate and New Red Sandstone of the 

 Bristol district. 



The Dolomitic Conglomerate contains the bones of Dinosaurian 

 reptiles discovered in Durdham Down, and preserved in this 

 Museum ; they were described by Dr. Riley and Mr. Stuchbury 

 in 1836,^ and were then the oldest Dinosauria in Britain. Since 

 that date the Triassic sandstones of Cheshire, Scotland, and 

 North America have been found to contain the foot-imprints of 

 Cheirotheria, and the same formation near Warwick the bones 

 and teeth of remarkable reptiles belonging to the family Laby- 

 rinthodontia ; subsequently it has been discovered that the coal- 

 field of Miinster-Appel in Rhenish Bavaria, and that of Saar- 

 briick between Strasburg and Treves, contain the skulls and 

 bones of several species of air-breathing reptiles which were 

 described by Goldfuss under the generic name Archegosatirus. 

 The reptilian remains of the conglomerate, though now not the 

 oldest of their class, still retain their interest for the Palaeonto- 

 logist, as they prove that highly organised Dinosauria lived on 

 Triassic land. I must refer you to the original memoir for a full 

 account of these bones, which enabled its authors to establish two 

 genera for them. The one, Thecodontosaurus, has the teeth 

 placed closely together in the jaw-bones. They are sharp, 

 conical, compressed, and have their anterior and posterior borders 

 finely denticulated, and the extremity slightly bent, like the teeth 

 of Megalosa'urus. Falaosaunis has the teeth compressed and 

 pointed likewise ; but one of the borders only is denticulated, 

 and the other trenchant. The species are distinguished by the 

 size and form of the teeth. The vertebrae resemble those of 

 Teleosaurus in being contracted in the middle, and having their 

 articular surfaces slightly biconcave ; and the rest of the bones 

 of the skeleton resemble the forms of the Lacertian type. 



We know very little of the life of the Trias in the district 

 under consideration, beyond the reptilian remains first noticed 

 here, until we come to the close of this age, when we find upper 

 grey marls of the Keuper overlain by and passing into a series 

 of black shales and limestones known as the Avicida conturta or 

 Rhoetic beds, which have a great interest for us, as they comprise 

 the famous Bone-bed of Aust Cliff known to all geologists. The 

 leading fossils are Avicula contorta, Cardium Rhceticum, Monotis 

 decussata, Fecten Valoniensis, and the small crustacean, Estheria 

 mimtta. The fishes are Nemacanthus, Saurichthys, Hybodjis, 

 ' Trans. Geol. Soc. and series, vol. v. p. s-^P (1840). 



