The little land-shell already noticed as having been detected by Sir Charles Lyell in the carboniferous rocks of Nova Scotia, seems to be as yet the only air-breathing mollusc obtained from rocks of such high antiquity. Insect remains have been detected in the English coal-fields belonging to two or three species of beetles; while on the Continent, wing-sheaths and other fragments of cockroaches, scorpions, grasshoppers, locusts, crickets, &c., have been detected. But the most remarkable traces of air-breathers consist in various indications of the existence of reptiles during the Carboniferous era. Fragmentary skeletons, with detached bones and plates, have been found in Bavaria and America, together with long tracks of footprints, from which it appears that during the time our coal-seams were forming, there swam through the sluggish deltas, or crept amid the dank luxuriant foliage, strange lizard-like forms, large enough to leave behind them on the soft yielding mud or sand the impress of their double pair of toed feet. But of these animals we have much to learn. Some of them have bequeathed to us merely their dismembered broken bones; others have left but the imprints of their toes. Yet even these remains, trifling as they may seem, become of importance when we remember that they demonstrate fishes not to have been the highest types of being during the epoch of the Coal, and show that while the bulky holoptychius held the supremacy of the waters, lizard-like forms of a less formidable type seem, so far as we know, to have ruled it over the land.