Between reptiles and fishes an intermediate type has been found in the Archegosaurus of the Coal formation; while the Labyrinthodon of the Trias combined characters of the Batrachia with those of crocodiles, lizards, and ganoid fishes. Even birds, the most apparently isolated of all living forms, and the most rarely preserved in a fossil state, have been shown to possess undoubted affinities with reptiles; and in the Oolitic Archæopteryx, with its lengthened tail, feathered on each side, we have one of the connecting links from the side of birds; while Professor Huxley has recently shown that the entire order of Dinosaurians have remarkable affinities to birds, and that one of them, the Compsognathus, makes a nearer approach to bird organisation than does Archæopteryx to that of reptiles.
Analogous facts to those occur in other classes of animals, as an example of which we have the authority of a distinguished paleontologist, M. Barande, quoted by Mr. Darwin, for the statement, that although the Palæozoic Invertebrata can certainly be classed under existing groups, yet at this ancient period