forms; amphibamus, raniceps, dendrerpeton, hylonomus, baphetes, and sauropus are found in the coal measures of Nova Scotia and the United States. Footprints of labyrinthodonts are known in the coal measures of Pennsylvania, Illinois, Indiana, and Kansas. The genus lepidotosaurus is known in two species in the Permian of Europe. The labyrinthodon (cheirotherium), anisopus, otozaum, macropteria, telerpeton, and other amphibians occur in the trias.
Class Reptilia. The order lacertia is represented in the Permian by the genera protosaurus, palæosaurus, deuterosaurus, and thecodontosaurus; the last is one of the most highly organized forms of the order. The genera rhynchosaurus, clepsysaurus, belodon, phytosaurus, rhabdopelix, and others, are characteristic of the trias of Europe and America. Other genera are known in the Jurassic and cretaceous, and in the present period. The genus mosasaurus, beginning in the cretaceous, is most conspicuous among the saurians of that period, occurring in numerous localities and in many species. Of the order crocodilia, the genera teleosaurus, hyposaurus, thoracosaurus, holops, and mystriosaurus are examples. The order begins in the trias, and continues to the present time, the true crocodiles occurring in the tertiary. The order pterosauria (flying saurians) are represented by the genera pterodactylus, rhamphorhynchus, and ornithopterus, beginning in the lias and disappearing with the cretaceous. The order dinosauria, represented by the genera iguanodon, megalosaurus, anomæpus, bathygnathus (an amphibian?), hadrosaurus, hylæosaurus, and others, begin their existence in the trias, and continue to the base of the cretaceous period in Europe and America. The order dicynodonta is a remarkable group of saurians, represented by dicynodon, ouedenodon, and others, in supposed triassic rocks of south Africa and Bengal. The enaliosaurians (sea lizards), including plesiosaura and ichthyosaura, began their existence in the trias, disappearing with the cretaceous. The genera nothosaurus, limosaurus, and sphenosaurus are among the triassic forms; and ichthyosaurus and plesiosaurus are characteristic liassic forms, occurring also in cretaceous. To the same order belong the discosaurus and polycoteles of the American cretaceous. The ophidia (serpents) make their first appearance in the eocene tertiary, and continue in all the more modern epochs. The genus palæophis is characteristic of European and American tertiary; and lithophis, limnophis, and dinophis have been described from American tertiary. The chelonia (turtles, tortoises) begin their existence in the middle of the Jurassic period, and continue to the present time. The earliest forms were of marine habitat, but at later periods we find freshwater and land forms. The tretosternum is the earliest well established genus. A monstrous form, atlantochelys, and other large and small turtles, occur in the cretaceous of Kansas. The genera trionyx, emys, compremys, colossochelys, and others occur in the tertiary.
Class Aves. The existence of birds has been inferred from the occurrence of three-toed tracks in the sandstone of the Connecticut valley of the age of the trias (?). A remarkable genus of birds, the archæopteryx, has been found in the Jurassic slates of Solenhofen. The genera termatornis, palæotringa, laornis, ichthyornis, apatornis, and others, have been described from the cretaceous. Fossil birds occur in the Wealden of Europe, and numerous genera and species in the tertiary of Europe and America. The miocene beds of France afford more than 70 species.
Class Mammalia. The marsupialia were the first in geological order among the mammalia, the genus microlestes occurring in the upper trias of Germany and England. The dromatherium sylvestre of Emmons is a small marsupial animal from the trias of North Carolina. The spalacotherium, amphitherium, and phascolotherium have been found in beds of the Jurassic age; while other forms are known in the tertiary. The cetacea appear in the American eocene period in the gigantic genus zeuglodon. Other forms occur in the miocene of the Atlantic coast; and the skeleton of a small whale, beluga, has been found in the post-pliocene of the Champlain valley. Of the order unqulata, the palæotherium, anaplotherium (xiphodon), and lophiodon were the earliest representatives in the eocene of Europe; and in the same formation in America, we have the genera hyrachyus and palæosyops, belonging to the same group as the preceding; the uintatherium and dinoceras, which belong to the rhinocerata; and the orohippus of the equidæ. In the miocene we have the genera anchitherium, hipparion, titanotherium. rhinoceras, oreodon, brontotherium, and others. The horse, camel, llama, deer, musk ox. hog, tapir, hippopotamus, and other forms are represented in that epoch, and are continued to the present time. The genus bos occurs only in the latest tertiary or quaternary. Of the proboscidæ, we have the dinotherium, mastodon, and elephas in the upper miocene; but the elephant and mastodon are more characteristic of the pliocene and later formations. The carnivora begin their existence in the tertiary. Among the earliest forms are arctocyon and palæocyon in the eocene; the genera hyænodon, machærodus, felis, canis, cynodon, amphicyon, ursus, hyæna, and others, occur in the later epochs of the system. Of the rodentia, the genera arctomys, lepus, mus, castor, arvicola, lagomys, and others, occur in the later tertiary. The cheiroptera, or bat-like animals begin their existence in the later tertiary; as also the insectivora proper, none of them appearing before the later miocene.
—The following synopsis of the classification of plants will serve for general reference in palæontology:
CRYPTOGAMOUS OR FLOWERLESS PLANTS.
Class I. Anophytes, and II. Thallophytes or cellular cryptogams.
Musci, hepaticæ, lichens, fungi, algcæ, desmidieæ.
Class III. Acrogens, or vascular cryptogams.
Equisetaceæ., filices, lycopodiaceæ, hydropteridæ.
PHENOGAMOUS OR FLOWERING PLANTS.
Class IV. Endogens or Monocotyledons.
The orders of this class include the cyperaceæ (sedge), gramineæ (grasses), juncaceæ (bulrushes), liliaceæ (lilies), typhaceæ (cattail), palmaceæ (palms), and many others.
Class V. Exogens or Dicotyledons.
Under the subclass of angiospermous plants (seeds in a pericarp) are included more than 100 orders, which em- brace all the ordinary forest trees except the coniferæ, besides far the greater proportion of flowering plants. Under the subclass of gymnosperms (seeds naked) are included all the coniferæ.
Until near the end of the Silurian period, the only remains of plants are of marine origin, such as algæ or fucaceæ; while some of the forms classed as plants may be really sponges. The earliest evidence of dry-land vegetation began with those conditions which ushered in the Devonian epoch; for the general character of the flora in the Devonian of America, so far as known, remains essentially the same throughout the carboniferous period. Here we have land plants of acrogenous forms, such as ferns in great abundance; the equisetaceæ in the calamites; the lycopodiaceæ in the lycopodites, lepidodendron, &c.; while psaronius, stigmaria, sigillaria, and others constitute orders allied to those mentioned. During this period the phenogamous plants are comparatively rare, and these are of the coniferæ. The condition of the surface favored only the development of the lower orders of vegetation; and we know that the low land of this period was subject to the influx of the ocean, probably from oscillations of the continental land, giving alternate strata of land deposits with land plants, and marine calcareous strata with shells and marine remains alone. The great amount of land vegetation at this period does not indicate that the entire surface of the present continent was then dry land, and that plants everywhere abounded at the same time and are imbedded in strata of this age. On the contrary, at the west and southwest, land plants are extremely rare, or altogether wanting in rocks of this period; while strata of marine origin with marine animal remains hold the same position. At each successive geological period the flora appears to have approached more nearly that of the present; not however
