such as birds and mammals back into the Palaeozoic era, and to claim that no order of plants had ever gone extinct. Much paper has been consumed by historians of science ruminating on this strange and somewhat unclear idea. Huxley was wrong to pitch the loss of orders in the Phanerozoic as low as 7%, and he did not estimate the number of new orders which evolved. Persistent types sat rather uncomfortably next to Darwin's more fluid ideas; despite his intelligence, it took Huxley a surprisingly long time to appreciate some of the implications of evolution. However, gradually Huxley moved away from this conservative style of thinking as his understanding of palaeontology, and the discipline itself, developed. Huxley's detailed anatomical work was, as always, first-rate and productive. His work on fossil fish shows his distinctive approach: Whereas pre-Darwinian naturalists collected, identified, and classified, Huxley worked mainly to reveal the evolutionary relationships between groups. The lobed-finned fish (such as coelacanths and lung fish) have paired appendages whose internal skeleton is attached to the shoulder or pelvis by a single bone, the humerus or femur. His interest in these fish brought him close to the origin of tetrapods, one of the most important areas of vertebrate palaeontology. The study of fossil reptiles led to his demonstrating the fundamental affinity of birds and reptiles, which he united under the title of Sauropsida. His papers on Archaeopteryx and the origin of birds were of great interest then and still are. Apart from his interest in persuading the world that man was a primate, and had descended from the same stock as the apes, Huxley did little work on mammals, with one exception. On his tour of America Huxley was shown the remarkable series of fossil horses, discovered by O. C. Marsh, in Yale's Peabody Museum. An Easterner, Marsh was America's first professor of palaeontology, but also one who had come west into hostile Indian territory in search of fossils, hunted buffalo, and met Red Cloud (in 1874). Funded by his uncle George Peabody, Marsh had made some remarkable discoveries: the huge Cretaceous aquatic bird Hesperornis, and the dinosaur footprints along the Connecticut River were worth the trip by themselves, but the horse fossils were really special. After a week with Marsh and his fossils, Huxley wrote excitedly, "The collection of fossils is the most wonderful thing I ever saw." The collection at that time