We may, for convenience, call these animals reptiles, but they are regarded as belonging to that lower grade of reptilian animals, the Amphibians or Batrachians, which includes the modern frogs and newts and water-lizards.[56] Still it would be doing great injustice to the carboniferous reptiles not to say, that while related to this low type, they presented a much greater range of organisation than it shows at present, evincing a capability to fill most of the places now occupied by the true reptiles. Some of them were aquatic, and with limbs rudimentary or little developed, but many of them walked on the land, and were powerful and predaceous creatures. They had large and complex teeth, they were protected by external bony plates, and some of them had in addition a beautiful covering of horny plates and spines, and ornamental lappets. Many had well-developed ribs, indicating a condition of respiration much in advance of that in the ribless batrachians. Some of them attained to size and strength rivalling those of the modern alligators, while some of the smallest species exhibit characters approaching in some respects to the lizards. Perhaps the most fish-like of these animals are those first discovered by von Dechen (_Archegosaurus_, Fig. 134). Their long heads, short necks, supports for gills, feeble limbs and long flat tail, show that they were aquatic creatures presenting many points of resemblance to the Ganoid fishes which must have been their companions. Yet they show what no fish can exhibit, fore and hind limbs with proper toes, and the complete series of bones that appear in our own arms and legs, while they must have had true lungs and breathed through nostrils. So different are they from the fish in details, that a single limb bone, a vertebra, a rib, or a fragment of a skull bone, suffices to distinguish them. Much has been said recently of the genesis of limbs; and here, as far as now known, we have the first true limbs; but it is scarcely too much to say that the feet of _Archegosaurus_ differ more from the fins of any carboniferous fish than they do from the human hand; while it is certain that the feet which made the impressions represented in Fig. 133, on the lowest beds of the Carboniferous, or that from the upper coal-formation represented in Fig. 139, were not less typical or perfectly formed feet than those of modern lizards. Leaving these fish-like forms, we find the remainder of the carboniferous reptiles to diverge from them along three lines. [Illustration: FIG. 134.—_Archegosaurus Decheni._ Head and anterior limb reduced. Coal-field of Saarbruck.] [Illustration: FIG. 135.—_Ptyonius._ A Snake-like Amphibian. Coal-measures of Ohio.—After Cope.]