The study of the forms of life no longer existing on the earth, from the scanty remains preserved to us, has provoked a very great interest almost from the commencement of historical times. The very small portion of this vast field I am treating of in the following pages has a special attraction, as it deals to a great extent with forms familiar in a living state to our immediate forefathers and even to some of ourselves. Although I have here arranged the species systematically, they fall into two distinct categories, namely those known externally as well as internally, and those of which we know bones and egg-shells only. Under the former category might be included those merely known from descriptions or figures in ancient books, as well as those of which specimens exist. In the present work several plates have been reconstructed from such descriptions in order to give some idea of their probable appearance. There is considerable difference of opinion as to the approximate date of the disappearance of many of the species known from bones dug from deposits which have been variously determined as pleistocene and post-pleistocene. It seems to me that this problem can never be entirely solved, but the significant fact remains, that while many bones of these species in one locality have been collected in the kitchen-middens of the former inhabitants, in other localities the same bones occur in what seem to be much older formations. In view of this and kindred facts, I have mentioned many species which some ornithologists will probably consider outside the range of the present treatise, viz., birds which have become extinct in the last seven- or eight-hundred years. Taking my first category, viz., those species whose exterior is more or less known, our knowledge is very variable in scope; about some we have a very full and even redundant literature, such as the Great Auk, the Labrador Duck, and Notornis, while of others, such as most of the extinct Parrots from the West Indies, the "Giant" of Mauritius, the "Blue Bird" of Bourbon, and so forth, we have the very scantiest knowledge. Even in the times of Leguat and Labat there must have been many species, now extinct, of which no mention has ever been made, for {viii} these old writers only mentioned such species which impressed themselves on their memories either from their size, peculiar shape, beauty of plumage, or excellence and usefulness for food--in fact the culinary property of the various birds seems to have been their principal interest. One of the most interesting phenomena connected with recently extinct birds is the resemblance of the fauna of the Mascarene Islands and that of the Chatham Islands in the possession of a number of large flightless Rails, though the significance of this fact has been much exaggerated.