Leaving now the English herbivorous Dinosaurs, we pass on to those still more wonderful forms discovered of late years by Professor Marsh. The former have been treated at considerable length, first because they are English, and, as such, the history of their discovery possesses considerable interest; secondly, because their elucidation reflects the highest credit on our great pioneers in this fruitful field of research, and illustrates the manner in which great naturalists have been able to draw most important and wonderful conclusions (afterwards verified in most cases) from material apparently far from promising. For example, Cuvier's prophecy of the Iguanodon from a few teeth is a striking example of the result of reasoning from the known to the unknown, an example which seems to us worthy to be ranked with the discovery of Neptune by Adams and Leverrier, or, to take a more recent case, the discovery by Mendeleef of the Periodic Law, by means of which he has foretold the discovery of new chemical elements. Whatever may have been the origin of the great mammalian class, the possibility and even probability of birds and Dinosaurs being descended from a common ancestor is a theory for which much may be said, and it has been adopted by many leading naturalists of the present day, who have been convinced by Professor Huxley's clear elucidation of the nature of the pelvic region in the group of Dinosaurs which has been above described (the Ornithopoda, or bird-footed group). It was Professor Huxley who first propounded this interesting speculation, basing his belief on the many bird-like characters presented by this strange group of extinct reptiles--the small head and fore limbs, the long and often three-toed hollow hind limbs, the bones of the pelvis or haunch, their habit of walking in a semi-erect position on those limbs (as proved by their tracks), and in some of hopping, as the little Compsognathus most probably did. And, last but not least, the strange mixture of bird-like and reptilian characters presented by certain most anomalous birds discovered by Professor Marsh in American Cretaceous rocks, viz. the huge Hesperornis and the smaller Ichthyornis. Speaking on this subject some years ago, Professor Marsh said, "It is now generally admitted by biologists who have made a study of vertebrates, that birds have come down to us through the Dinosaurs, and the close affinity of the latter with recent struthious birds (ostrich, etc.), will hardly be questioned. The case amounts almost to a demonstration, if we compare with Dinosaurs their contemporaries, the Mesozoic birds. The classes of birds and reptiles, as now living, are separated by a gulf so profound that a few years since it was cited by the opponents of Evolution as the most important break in the animal series, and one which that doctrine could not bridge over. Since then, as Professor Huxley has clearly shown, this gap has been virtually filled by the