A Text-Book of Mammals 1

Abstract

FEW branches of zoological science have made greater advances during the last ten or a dozen years than has the study of mammals. Investigations with the microscope and the section-cutter have revolutionised our ideas as to the homology and succession of the dentition of the marsupials, while our conception of the relationship of that group to the monotremes on the one hand, and to the typical placentals on the other, has been totally altered by the discovery of a vestigial placenta in the bandicoots, and also by the apparent evidence of a connection with the creodonts afforded by certain extinct types from the South American Tertiaries. Then, again, the systematic part of the subject has been enriched by the discovery of a number of totally new and unexpected living generic types, such as Notoryctes and Cænolestes among the marsupials, Zenkerella and Idiurus among the scaly-tailed African squirrels, and Ocapia among the ungulates. Our conceptions of species and local races have undergone an equally profound change in the group under consideration, and the number of such new forms—some good and some bad—which have been added to our lists during the last few years is little short of astonishing. Moreover, trinomialism has been introduced into the science, and is largely adopted by a considerable number of eminent writers; and nomenclature itself has undergone a change which, while in many respects regrettable, could scarcely have been avoided, at least to a certain degree, if zoology is to maintain any semblance of consistency. Neither have the palæontologists been idle during the period referred to, the wonderful extinct mammalian fauna of Patagonia—inclusive of the ground-sloth, whose skin was recently found in a cave at Ultima Esperanza—having been to a large extent described during the last decade, while many interesting forms of extinct mammalian life have been made known from other parts of the world. If to the above be added the change of view with regard to the limits of zoological regions and the extent to which lands now widely sundered have been connected in past epochs of the world's history, there is little cause for wonder if the majority, or all, of the standard text-books dealing with mammals are more or less completely out of date.