The third line of progress leads to some slender and beautiful creatures (_Microsauria_), chiefly known to us by remains found in erect trees, and which resembled in form and habits the smaller modern lizards. They have simple teeth, a well-developed brain-case, limbs of some length, and bony and scaly armour, the latter in some cases highly ornate.[60] They were probably the most thoroughly terrestrial, and the most active of the coal batrachians, if indeed they were not strictly intermediate between them and the lizards proper. Fig. 138 shows some fragments of one of these animals; and the animal represented in Fig. 139, recently figured by Fritsch, probably belongs to this group. [Illustration: FIG. 138.—A lizard-like Amphibian (_Hylonomus aciedentatus_). _a_, Maxillary bone; enlarged. _b_, Mandible; enlarged. _c_, Teeth; magnified, showing front and side view of ordinary tooth and grooved anterior tooth. _d_, Section of tooth; magnified. _e_, Scale; natural size and magnified. _f_, Pelvic bone (?); natural size. _g_, Rib; natural size. _h_, Scapular bone (?); natural size. _i_, Palate; natural size.] [Illustration: FIG. 139.—_Stelliosaurus longicostatus_ (Fritsch). Upper Coal-formation of Bohemia.] The Labyrinthodonts of the Carboniferous continue upward into the Permian, where they meet with the true reptiles; and in the earlier Mesozoic some of the largest and most typical examples are found.[61] But here their reign ceases, and they give place to reptiles of more elevated type, whose history we must consider in the next chapter. Nothing can be more remarkable than the apparently sudden and simultaneous incoming of the batrachian reptiles in the Coal-formation. As if at a given signal, they came up like the frogs of Egypt everywhere and in all varieties of form. If, as evolutionists suppose, they were developed from fishes, this must have been by some sudden change, occurring at once all over the world, unless indeed some great and unknown gap separates the Devonian from the Carboniferous—a supposition which seems quite contrary to fact—or unless in some region yet unexplored this change was proceeding, and at a particular time its products spread themselves over the world—a supposition equally improbable. In short, the hypothesis of evolution, as applied to these animals, is surrounded with geological improbabilities.