to those found in the limbs of the higher Vertebrates.  All the Carboniferous Amphibians belong to a group which has now wholly passed away—­namely, that of the Labyrinthodonts.  In the marine strata which form the base of the Carboniferous series these creatures have only been recognised by their curious hand-shaped footprints, similar in character to those which occur in the Triassic rocks, and which will be subsequently spoken of under the name of Cheirotherium.  In the Coal-measures of Britain, the continent of Europe, and North America, however, many bones of these animals have been found, and we are now tolerably well acquainted with a considerable number of forms.  All of them seem to have belonged to the division of Amphibians in which the long tail of the young is permanently retained; and there is evidence that some of them kept the gills also throughout life.  The skull is of the characteristic Amphibian type (fig. 132, a), with two occipital condyles, and having its surface singularly pitted and sculptured; and the vertebrae are hollowed out at both ends.  The lower surface of the body was defended by an armour of singular integumentary shields or scales (fig. 132, c); and an extremely characteristic feature (from which the entire group derives its name) is, that the walls of the teeth are deeply folded, so as to give rise to an extraordinary “labyrinthine” pattern when they are cut across (fig. 132, b).  Many of the Carboniferous Labyrinthodonts are of no great size, some of them very small, but others attain comparatively gigantic dimensions, though all fall short in this respect of the huge examples of this group which occur in the Trias.  One of the largest, and at the same time most characteristic, forms of the Carboniferous series, is the genus Anthracosaurus, the skull of which is here figured.

No remains of true Reptiles, Birds, or Quadrupeds have as yet been certainly detected in the Carboniferous deposits in any part of the world.  It should, however, be mentioned, that Professor Marsh, one of the highest authorities on the subject, has described from the Coal-formation of Nova Scotia certain vertebrae which he believes to have belonged to a marine reptile (Eosaurus Acadianus), allied to the great Ichthyosauri of the Lias.  Up to this time no confirmation of this determination has been obtained by the discovery of other and more unquestionable remains, and it therefore remains doubtful whether these bones of Eosaurus may not really belong to large Labyrinthodonts.

LITERATURE.

The following list contains some of the more important of the original sources of information to which the student of Carboniferous rocks and fossils may refer:—­