English anatomist and biologist Richard Owen (1804-92), who in 1842 coined the word 'dinosaur', published this book in 1859, the year of On the Origin of Species. He reviews ancient and recent studies of mammals in Western science before going on to present his own updated categorisation of the class. Owen's eye for detail and range of scholarship are evident in this work, which is an extensive catalogue of mammals based on biological, geographical and anatomical characteristics. It incorporates, among other things, detailed classifications and sub-classifications of genus based on dental structures, food habits and cerebra. Owen's prose is lucid and precise and his investigations scrupulous, demonstrating the commitment that led him to become one of the foremost anatomists of his time. An appendix reveals Owen's views on the hotly debated theories of transmutation and extinction proposed by scientists such as Lamarck, Lyell and Darwin.