No advance in this class of animals. The science testifies to no successive steps here. "They stood at the head of the icthyic division at the outset; but there has been, during these periods, a progressive _degeneracy_, so that though all possessed a high organization at first, there is found in the after creations a _succession of lapses_ until the division of fishes now contains species ranking little above the earth-worm." "A single well defined placoid fossil in the Bala limestone as fully proves the existence of placoid fishes, during the period of its deposition, as if the rock were made up of placoid fossils, for it is not a question of numbers, but of rank." The question, now, comes home to us with all its force, how did fishes of this high order come to exist before any of the inferior class?