Bristol will be considered as Triassic, thus leaving Protorosaurus as the principal and most important representative of * Fig. 138.-Protorosaurus Speneri, Middle Permian, Thuringia, reduced in size. (After Von Meyer.) [Copied from Dana.] the Permian Reptiles. The type-species of the genus Protorosaurus is the P. Speneri (fig. 138) of the "Kupfer-schiefer" of * Though commonly spelt as above, it is probable that the name of this Lizard was really intended to have been Proterosaurus-from the Greek proteros, first; and saura, lizard: and this spelling is followed by many writers. + In an extremely able paper upon the subject (Quart. Journ. Geol. Soc., vol. xxvi.), Mr Etheridge has shown that there are good physical grounds for regarding the dolomitic conglomerate of Bristol as of Triassic age, and as probably corresponding in time with the Muschelkalk of the Continent. Thuringia, but other allied species have been detected in the Middle Permian of Germany and the north of England. This Reptile attained a length of from three to four feet; and it has been generally referred to the group of the Lizards (Lacertilia), to which it is most nearly allied in its general structure, at the same time that it differs from all existing members of this group in the fact that its numerous conical and pointed teeth were implanted in distinct sockets in the jaws-this being a Crocodilian character. In other respects, however, Protorosaurus approximates closely to the living Monitors (Varanide); and the fact that the bodies of the vertebræ are slightly cupped or hollowed out at the ends would lead to the belief that the animal was aquatic in its habits. At the same time, the structure of the hind-limbs and their bony supports proves clearly that it must have also possessed the power of progression upon the land. Various other Reptilian bones have been described from the Permian formation, of which some are probably really referable to Labyrinthodonts, whilst others are regarded by Professor Owen as referable to the order of the "Theriodonts," in which the teeth are implanted in sockets, and resemble those of carnivorous quadrupeds in consisting of three groups in each jaw (namely, incisors, canines, and molars). Lastly, in red sandstones of Permian age in Dumfriesshire have been discovered the tracks of what would appear to have been Chelonians (Tortoises and Turtles); but it would not be safe to accept this conclusion as certain upon the evidence of footprints alone. The Chelichnus Duncani, however, described by Sir William Jardine in his magnificent work on the 'Ichnology of Annandale,' bears a great resemblance to the track of a Turtle. No remains of Birds or Quadrupeds have hitherto been detected in deposits of Permian age. LITERATURE. The following works may be consulted by the student with regard to the Permian formation and its fossils : (1) "On the Geological Relations and Internal Structure of the Magnesian Limestone and the Lower Portions of the New Red Sandstone Series, &c."-"Trans. Geol. Soc.,' ser. 2, vol. iii. Sedgwick. (2) 'The Geology of Russia in Europe.' Murchison, De Verneuil, and Von Keyserling. (3) Siluria.' Murchison. 6 (4) Permische System in Sachsen.' Geinitz and Gutbier. (5) Die Versteinerungen des Deutschen Zechsteingebirges.' Geinitz. (6) 'Die Animalischen Ueberreste der Dyas.' Geinitz. (7) 'Monograph of the Permian Fossils of England' (Palæontographical Society). King. (8) 'Monograph of the Permian Brachiopoda of Britain' (Palæontographical Society). Davidson. (9) "On the Permian Rocks of the North-West of England and their Extension into Scotland"-"Quart. Journ. Geol. Soc.,' vol. xx. Murchison and Harkness. (10) Catalogue of the Fossils of the Permian System of the Counties of Northumberland and Durham.' Howse. (II) Petrefacta Germaniæ.' Goldfuss. (12) Beiträge zur Petrefaktenkunde.' Münster. (13) Ein Beitrag zur Palæontologie des Deutschen Zechsteingebirges.' Von Schauroth. (14) Saurier aus dem Kupfer-schiefer der Zechstein-formation.' Von Meyer. (15) Manual of Paleontology.' Owen. (16) Recherches sur les Poissons Fossiles.' Agassiz. (17) Ichnology of Annandale.' Sir William Jardine. (18) Die Fossile Flora der Permischen Formation.' Goeppert. (19) Genera et Species Plantarum Fossilium.' Unger. (20) "On the Red Rocks of England of older Date than the Trias" —‘Quart. Journ. Geol. Soc.,' vol. xxvii. Ramsay. CHAPTER XV. THE TRIASSIC PERIOD. We come now to the consideration of the great Mesozoic, or Secondary series of formations, consisting, in ascending order, of the Triassic, Jurassic, and Cretaceous systems. The Triassic group forms the base of the Mesozoic series, and corresponds with the higher portion of the New Red Sandstone of the older geologists. Like the Permian rocks, and as implied by its name, the Trias admits of a subdivision into three groups a Lower, Middle, and Upper Trias. Of these subdivisions the middle one is wanting in Britain; and all have received German names, being more largely and typically developed in Germany than in any other country. Thus, the Lower Trias is known as the Bunter Sandstein; the Middle Trias is called the Muschelkalk; and the Upper Trias is known as the Keuper. I. The lowest division of the Trias is known as the Bunter Sandstein (the Grès bigarré of the French), from the generally variegated colours of the beds which compose it (German, bunt, variegated). The Bunter Sandstein of the continent of Europe consists of red and white sandstones, with red clays, and thin limestones, the whole attaining a thickness of about 1500 feet. The term "marl" is very generally employed to designate the clays of the Lower and Upper Trias; but the term is inappropriate, as they may contain no lime, and are therefore not always genuine marls. In Britain the Bunter Sandstein consists of red and mottled sandstones, with unconsolidated conglomerates, or "pebble-beds," the whole having a thickness of 1000 to 2000 feet. The Bunter Sandstein, as a rule, is very barren of fossils. II. The Middle Trias is not developed in Britain, but it is largely developed in Germany, where it constitutes what is known as the Muschelkalk (Germ. Muschel, mussel; kalk, limestone), from the abundance of fossil shells which it contains. The Muschelkalk (the Calcaire coquillier of the French) consists of compact grey or yellowish limestones, sometimes dolomitic, and including occasional beds of gypsum and rock-salt. III. The Upper Trias, or Keuper (the Marnes irisées of the French), as it is generally called, occurs in England; but is not so well developed as it is in Germany. In Britain, the Keuper is 1000 feet or more in thickness, and consists of white and brown sandstones, with red marls, the whole topped by red clays with rock-salt and gypsum. The Keuper in Britain is extremely unfossiliferous; but it passes upwards with perfect conformity into a very remarkable group of beds, at one time classed with the Lias, and now known under the names of the Penarth beds (from Penarth, in Glamorganshire), the Rhætic beds (from the Rhætic Alps), or the Avicula contorta beds (from the occurrence in them of great numbers of this peculiar Bivalve). These singular beds. have been variously regarded as the highest beds of the Trias, or the lowest beds of the Lias, or as an intermediate group. The phenomena observed on the Continent, however, render it best to consider them as Triassic, as they certainly agree with the so-called Upper St Cassian or Kössen beds which form the top of the Trias in the Austrian Alps. The Penarth beds occur in Glamorganshire, Gloucestershire, Warwickshire, Staffordshire, and the north of Ireland; and they generally consist of a small thickness of grey marls, white limestones, and black shales, surmounted conformably by the lowest beds of the Lias. The most characteristic fossils which they contain are the three Bivalves Cardium Rhæticum, Avicula contorta, and Pecten Valoniensis; but they have yielded many other fossils, amongst which the most important are the remains of Fishes and small Mammals (Microlestes). In the Austrian Alps the Trias terminates upwards in an extraordinary series of fossiliferous beds, replete with marine. fossils. Sir Charles Lyell gives the following table of these remarkable deposits : Strata below the Lias in the Austrian Alps, in descending order. 1. Koessen beds. (Synonyms, Upper St Cassian beds of Escher and Merian.) 2. Dachstein beds. 3. Hallstadt beds 4. A. Guttenstein beds. Grey and black limestone, with calcareous marls having a thickness of about 50 feet. Among the fossils, Brachiopoda very numerous; some few species common to the genuine Lias; many peculiar. Avicula contorta, Pecten Valoniensis, Cardium Rhæticum, Avicula inæquivalvis, Spirifer Münsteri, Dav. Strata containing the above fossils alternate with the Dachstein beds, lying next below. White or greyish limestone, often in beds three or four feet thick. Total thickness of the formation above 2000 feet. Upper part fossiliferous, with some strata composed of corals (Lithodendron.) Lower portion without fossils. Among the characteristic shells are Hemicardium Wulfeni, Megalodon triqueter, and other large bivalves. Red, pink, or white marbles, from 800 to 1000 feet in thickness, containing more than 800 species of marine fossils, for the most part mollusca. Many species of Orthoceras. True Ammonites, besides Ceratites and Goniatites, Belemnites (rare), Porcellia, Pleurotomaria, Trochus, Monotis salinaria, &c. A. Black and grey lime. stone 150 feet thick, alternating with the underlying Werfen beds. B. Red and green shale and sandstone, with salt and gypsum. Among the fossils are Ceratites cassianus, Myacites fassaensis, Naticella costata, &c. In the United States, rocks of Triassic age occur in several areas between the Appalachians and the Atlantic seaboard; but they show no such triple division as in Germany, and their exact place in the system is uncertain. The rocks of these areas consist of red sandstones, sometimes shaly or conglomeratic, occasionally with beds of impure limestone. Other more extensive areas where Triassic rocks appear at the surface, are found west of the Mississippi, on the slopes of the Rocky Mountains, where the beds consist of sandstones and gypsiferous |