March 1, 1886.] 



♦ KNOAVLEDGE ♦ 



139 



fresli, divided by low ridges —bases of future mountain 

 chains — and dotted ■witb islands ; numerous rivers 

 traversing tbe land and silting up lagoons and lakes 

 ■with the dehris worn from older rocks. Vegetation 

 flourished apace on these river banks and marshy flats, 

 and, with intermittent subsidence of the soil occurring 

 again and again, was buried under sand and mud, and 

 changed into coal of varying seams of thickness. Hence 

 the abundance of this mineral in the Carboniferous strata, 

 which, as a whole, yield more of value and variety for the 

 service of mau thau all the other systems put together. 

 Sandstones for building, marbles for decoration, metals 

 for machinery, coals wherewith to drive them, purest oil 

 from muddy shale, loveliest colours from tar, jet for the 

 lapidary's art — these are the rich gifts of the deep rocks. 



Of the plants forming the coal-measures, the larger 

 number are obliterated, but they all belong to the lower 

 orders, as do the club-mosses, tree-ferns, and other forms, 

 which, in the warm, moist atmosphere of those times, 

 reached a gigantic size, and had a worldwide range, even 

 far into Polar regions, where coal-seams have been found. 

 Of the animal life that dwelt amongst them w^ know 

 very little, nor do the extant fragments represent a tithe 

 of the forms then flourishing ; in the later deposits the 

 lower sub-kingdoms are represented by spiders and large 

 scorpions; by land-snails, beetles, may-flies, and other 

 insects ; while the first-known land vertebrates appear 

 iu the salamander-like and long-extinct amphibians 

 called Labyriuthodonts, from the labyrinthine structure 

 of their teeth. 



As usual, the marine remains are domiuant. The 

 lower tyjjes persist ; the trilobites are on the verge of 

 extinction, but higher forms of the same group, allied 

 more nearly to the lobster and the shrimp, succeed. 

 Forerunners of the beautiful ammonites appear, and the 

 fish, while still of the armoured species, have a more 

 reptilian character than their Devonian ancestors. 



The life-features of the Permian system, the last 

 division of the Primary epoch, difi:'er but little from those 

 of the Carboniferous ; the only, although important, dis- 

 tinction is iu the remains of true reptiles with crucodile- 

 Hke characters. 



We now leave the Primary epoch, and enter the 

 Secondary epoch, with its widely difl:'erent features and 

 contents, ex[ilicable only by a great break in the succes- 

 sion of strata, and by an enormous lapse of time for the 

 modification of the life-forms. Although, as in every 

 period, volcanic action is manifest, the igneous rocks 

 being pushed through the strata, or now and again 

 alternating with them, we meet with few traces of the 

 metamorphism which so balfles examination of the earlier 

 rocks ; we can mark more definitely the botmdaries of 

 laud and water ; measure more accurately the changes ; 

 and trace more clearly the relations between the succes- 

 sive life-forms, of which the marine are the preponderat- 

 ing, and the reptilian the most marvellotts. 



In the earliest division of this epoch, the Triassic, 

 many of the leading PahBOzoic types are extinct. Several 

 plants of the Coal and Permian systems have disappeared, 

 and the flora consists mainly of ferns, of cycads or palm- 

 ferns, and of conifers, or pines and firs, to which the 

 cycads are allied. Among the invertebrate animals, 

 certain molluscs are no longer found, but there is an 

 intermingling of old and new types. Oysters and whales 

 and members of the cuttle-fish group are abundant. As 

 yet the fi.shes show no marked advance in structure, and 

 the Amphibia are changed only in size, as their enormous 

 footprints show. Reptiles allied to the crocodile 



grottp are now the dominant type ; and sea-lizards, which 

 attained gigantic size in later periods. Whether certain 

 bipedal footprints in the Triassic sandstones are those of 

 birds is doubtful; perhaps they are tracks of reptiles with 

 bird-like movements. But, in the absence of proof that 

 they are due to birds, which certainly preceded mammals 

 in the succession of species, a great link is missing in the 

 Trias, since that system has yielded teeth of the earliest 

 known mammal. It was probably of the marsupial or 

 pouched species, a transitional form now represented 

 most nearly by the Australian phalangers and the 

 American oppossums. 



The Jurassic, or Oolitic, system occupies extensive 

 areas in both hemispheres, and ranges from the Arctic 

 circle to Australia. Its strata. Largely composed of coral 

 growths and other organic remains, are rich in special 

 life-forms which are limited to the Secondary ej)0ch. 



Its seas, which overspread the greater part of Euro])e, 

 covering the large salt lakes of the Trias, swarmed with 

 exquisite spiral ammonites, large and small ; with conical 

 holt-like belemnites, allied to the cuttle-fish group ; with 

 lobsters, prawns, and crabs, which succeeded the trilobites 

 and otlier crustaceans; with ganoid fishes, sharks, and 

 rays. And " there were giants in those days " ; monsters 

 of the deep in the ferocious sea-lizards, with their fish- 

 like bodits and flipper-like limbs ; monsters of the land, 

 too, of dread aspect and size seen neither before nor since; 

 one found in North American beds being, it is computed, 

 more than one htmdred feet in length and above thirty feet 

 in height. There were flying lizards, winged like bats, 

 hollow-boned like birds, and with claws, skin, and, teeth 

 like reptiles ; and it is in a Jurassic limestone strattim 

 that the oldest known true bird, a creature about the size 

 of a rook, is found. It does not correspond to any known 

 past or present birds, but represents a transitional type, 

 having both bird and reptile-like characters. In addition 

 to free claws to each wing, the tail is long, and made up 

 of .-eparate bones or prolonged vertebras, a feature noted 

 iu the embryos of birds and mammals, the significance 

 of which will appear later on. 



Therefore, while the sea, then, as ever, was the more 

 thickly peopled, the land had now a far more important 

 air-breathing population both of small things and great. 

 The hum of insect-life filled the cycadaceous forests, 

 butterflies sported in the sunshine, spiders spread their 

 webs for prey, and the remains of marsupials point 

 to the range of these small but highly-organised 

 creatures over Western Europe. The plants and animals 

 of these islands in Jurassic times probably resembled 

 those still found in Australia, which, by reason of its 

 long isolation from other continents, has preserved in its 

 pouched mammals, its sharks, its mud-fish, and its cycads, 

 more ancient life-forms than any other country. 



The vast chalk formations of the globe are the typical 

 features of the Cretaceous period (Lat. crcta, chalk), when 

 the sea overspread a large part of Europe, Asia and 

 Northern Africa, receiving on its floor the foramini- 

 feral shells which were converted into chalk, just as at 

 this day chalky ooze is being deposited at the bottom of 

 the Atlantic. Molluscs, nautiluses, belemnites, r.mmo- 

 nites, some of them the size of a cart-wheel, swivrmed in 

 its waters i and with them the huge reptiles (.f Jurassic 

 times, sea-lizards and sea-serpents, ganoids and sharks, 

 and, what is important to note, bony-skeletoned fish allied 

 to the salmon, lierriug, and perch families. 



In the North American formations, which have so 

 added to our knowledge of ancient life-forms, " dragons 

 of the prime," crocodile-like, bird-like, bat like, are 

 found, as also the remains of true birds, these last being 



