_Primates._--Among the vast number of extinct mammalia discovered in the Tertiary deposits of North America, no example of this order had been recognized up to 1872, when the discovery of more perfect remains showed, that a number of small animals of obscure affinities from the Lower Eocene of Wyoming, were really allied to the lemurs and perhaps also to the marmosets, the lowest form of American monkeys, but having a larger number of teeth than either. A number of other remains of small animals from the same formation, previously supposed to be allied to the Ungulata, are now shown to {133}belong to the Primates; so that no less than twelve genera of these animals are recognized by Mr. Marsh, who classes them in two families--Limnotheridæ, comprising the genera _Limnotherium_, (which had larger canine teeth), _Thinolestes_, _Telmatolestes_, _Mesacodon_, _Bathrodon_, and _Antiacodon_ of Marsh, with _Notharctos_, _Hipposyus_, _Microsyops_, and _Palæacodon_ previously described by Leidy;--and Lemuravidæ, consisting of the genera _Lemuravus_ (Marsh) and _Hyopsodus_ (Leidy). The animals of the latter family were most allied to existing lemurs, but were a more generalized form, _Lemuravus_ having forty-four teeth, the greatest number known in the order. These numerous forms ranged from the size of a small squirrel to that of a racoon. It is especially interesting to find these peculiar lemuroid forms in America, just when a lemur has been discovered of about the same age in Europe; and as the American forms are said to show an affinity with the South American marmosets, while the European animal is most allied to a West African group, we have evidently not yet got back far enough to find the primeval or ancestral type from which all the Primates sprang. About the same time, in the succeeding Miocene formation, true monkeys were discovered. Mr. Marsh describes _Laopithecus_ as an animal nearly the size of the largest South American monkeys, and allied both to the Cebidæ and the Eocene Limnotheridæ. Mr. Cope has described _Menotherium_ from the Miocene of Colorado, as a lemuroid animal, the size of a cat, and perhaps allied to _Limnotherium_. More Miocene remains will, no doubt, be discovered, by which we shall be enabled to trace the origin of some of the existing forms of South American monkeys; and perhaps help to decide the question (now in dispute among anatomists) whether the lemurs are really Primates, or form an altogether distinct and isolated order of mammalia.