In fine, then, no one can glance at a list of the carboniferous fauna without perceiving either that the animated world of that ancient epoch must have had a very different proportioning from what now obtains, or that we have only a meagre and fragmentary record of it. That the latter conclusion is the more philosophical will appear if we reflect upon the many chances that exist against the entombment and preservation of animal remains, especially of those peculiar to the land. How very small a proportion of the remains of animals living in our own country could be gathered from the surface-soil of any given locality, and how very inadequate would be the meagre list of species thus obtained, as representing the varied and extensive fauna of Great Britain! In contrasting, then, the rich abundance of marine organisms with the extreme paucity of terrestrial animals among the carboniferous rocks, it would be too hasty to infer a corresponding disproportion originally. It must be admitted that the rarity of air-breathers, after such long-continued and extensive explorations among terrestrial and lacustrine beds, presents a difficult problem, only (if at all) to be cleared away by patient and persevering investigation. With this preliminary caution, we may regard the carboniferous fauna as peculiarly rich in marine species. The sea-bottoms swarmed with stone-lilies, cup-corals, and net-like bryozoa, mingled with the various tribes of molluscan life--the brachiopods with their long ciliated arms; the bivalves and gastropods with their coloured shells that recall some of the most familiar objects of our shores; and the cephalopods with their groups of siphonated chambers, straight as in the orthoceras, or gracefully coiled as in the goniatite. The seas swarmed, too, with fishes belonging to the two great orders of ganoids and placoids, the latter represented now by our sharks and rays, though the exact type of the ancient genera is retained only by the cestracion or Port-Jackson shark; the ganoids, with their strong armour of bone, represented by but two genera, the lepidosteus of the American rivers, and the polypterus of the Nile,--two fishes that seem but as dwarfs when placed side by side with the gigantic holoptychius of the coal-measures. The rivers and estuaries of the same period seem to have been frequented by immense shoals of the smaller ganoidal fishes that fed on decaying matter brought down from the land, and perhaps, too, on the minute Crustacea that lay strewed by myriads along the bottom. Into these busy scenes the bulkier monsters from the sea made frequent migrations, perhaps in some cases ascending the rivers for leagues to spawn, and returning again to their places at the mouth of the estuary or in open sea. The rivers and lakes swarmed with small crustaceous animals, and nourished, too, shells like those of our pearl-mussels. The land--so luxuriantly clothed with vegetable forms--was hummed over