the Jurassic oolites, in which the records of life have been preserved in great abundance. The base of this series of formations corresponds with the upper portion of the New Red Sandstone, as the Permian series does

FIG. 17.-Lily Encrinite; from the Muschelkalk (Trias).

with its lower members. One of the first facts which strikes us here is the disappearance of several plants which were with us throughout the two preceding periods. Vegetation is now chiefly represented by ferns,

conifers, and cycads-the two last being plants of a distinctly higher order than those which have vanished. Marine invertebrate life is present in great force, but some hitherto numerous molluscan forms have become extinct, notably the productidæ. Among crinoids are the beautiful lily-encrinites of the Muschelkalk, decapod crustacea (lobsters) have their representives, pearl oysters abound, and chambered shells-goniatites, ammonites, ceratites, etc.—are plentiful; but the cephalopod shells, Belemnites, have not been known until now. The fishes still belong to the ganoid and placoid orders, with the exception of one genus, named by Agassiz Ceratodus, known only by its singular teeth, which are almost exactly like those of the existing "mud-fish" of tropical Australia, a fresh-water vegetable feeder. All the Triassic amphibia are believed to be labyrinthodonts, a group with which we became familiar in Carboniferous times. But some of these were of enormous size, as indicated by the footprints of one originally named the Cheirotherium, or "beast with a hand," on slabs of sandstone. A water-newt, with a skull three feet long and two broad and a body in proportion, would probably nearly represent this monster amphibian, though some anatomists have supposed it to be more nearly allied to the frogs or toads, from the character of its skull. But the body was certainly elongated, the hinder limbs longer and larger than the fore limbs, and the belly defended by bony plates. The footprints in the illustration are reduced to one-eighth of the natural size. It seems probable that the animal which left us these evidences

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of its presence had walked across a damp tract of sandy clay on the estuary of a river, and that this subsequently dried hard and even became cracked by the sun, as shown in the irregular transverse lines. The place might then have been covered by the wind with dry

FIG. 18.-Footprints of Labyrinthodon; occur in the flaggy sandstones of Britain, Germany, and North America (Trias). (Reduced.) sand, and subsequently overlaid by a fresh deposit during a flood or the return of the tide.

With the Triassic period begins that extraordinary influx of reptilian life, which increases throughout the

Jurassic and Cretaceous periods, and has given to the Secondary era the appropriate title of the " Age of Reptiles." Among these reptiles were some of most remarkable structure, suggesting affinities with turtles and crocodiles, and bearing in some instances additions to the upper jaw, like the canines of carnivorous animals. Such was the character of Dicynodon. But Cynodraco possessed not only canines, but incisors and molars of carnivorous type. In Rhynchosaurus the skull is similar to that of an aquatic bird, the jaws having been probably covered with a horny sheath; and the head of Oudenodon carried a pair of trenchant jaws without teeth. Among crocodilian forms are Nothosaurus, whose jaws were extremely long and furnished with numbers of sharp, pointed teeth set in distinct sockets, the head being carried on a long neck; and Simosaurus, remarkable for the great size of its orbits. To these may be added the genera Thecodontosaurus and Belodon; while the lizards are represented by the genera Telerpeton and Hyperodapedon.

Another series of footprints in the sandstone rocks of the Triassic system in Connecticut, has given rise to much discussion. Are they the tracks of a bird or a reptile? In the first place, it will be seen, on reference to Fig. 19, that the foot has three toes, of which the joints also correspond in number to those of a bird, and the general appearance of the footprint bears out the conclusion that it was made either by a heron, or crane, or some similar inhabitant of sea or river shores. If this were so, the bird must have been a veritable

colossus, for some of the largest of these footprints are over twenty inches long and twelve inches broad. On the other hand, no bird-bones, only those of reptiles, have been found in association with these tracks; and we know that in this and the Jurassic periods the characters of reptiles in many respects approximated to

FIG. 19.-Footprint of bird (or reptile ?) from the Triassic sandstone of the Connecticut river, America (reduced).

those of birds; and it is not impossible that we have here the impression of the hind foot of a huge reptile of terrestrial habits, which may have usually walked upon the hind legs. Still, as against this view, it should be noted that the tracks far more frequently consist of two than of. four feet; and, although the Deinosauria (dreadful lizards) possessed, at least in some instances, massive hinder limbs, with comparatively slight fore legs, and were mainly terrestrial in habit, it is difficult to believe the mode of progression on two legs