These species differ from each other in size, the smallest being scarcely so large as a lamb of three months, and in various circumstances connected with the form of their teeth, which it would be too tedious and minute to detail here. The _Anoplotheria_ have hitherto been discovered nowhere but in the gypsum quarries of the neighbourhood of Paris. They have two characters which are observed in no other animal; feet with two toes, the metacarpal and metatarsal bones of which are separate in their whole length, and do not unite into a single piece, as in the ruminantia; and teeth placed in a continuous series without any interruption. Man alone has the teeth so placed in mutual contiguity, without any interval. Those of the anaplotheria consist of six incisors in each jaw, a canine tooth and six grinders on each side, both above and below; their canine teeth are short and similar to the outer incisors. The three first grinders are compressed; the four others are, in the upper jaw, square, with transverse ridges, and a small cone between them; and, in the lower jaw, in the form of a double crescent, but without neck at the base. The last has three crescents. Their head is of an oblong form, and does not indicate that the muzzle has terminated either in a proboscis or a snout. This extraordinary genus, which can be compared to nothing in living nature, is subdivided into three subgenera: the _Anaplotheria_, properly so called, the anterior molares of which are still pretty thick, and the posterior ones of the lower jaw have their crescents with a simple ridge; the _Xiphodons_, of which the anterior molares are thin and sharp on the edges, and the under posterior, have, directly opposite the concavity of each of their crescents, a point, which, on being worn, also assumes the form of a crescent, so that then the crescents are double as in the ruminantia; lastly, the _Dichobunes_, the outer crescents of which are also pointed at the beginning, and which have thus points disposed in pairs upon their lower posterior grinders. The most common species in our gypsum quarries (_An. commune_), is an animal of the height of a boar, but much more elongated, and furnished with a very long and very thick tail, so that altogether it has nearly the proportion of the otter, but larger. It is probable that it was well fitted for swimming, and frequented the lakes in the bottom of which its bones have been incrusted by the gypsum which was deposited there. We have one a little smaller, but in other respects pretty similar (_An. secundarium_.) We are as yet acquainted with only one _xiphodon_, which, however, is a very remarkable animal: it is that which I have named _An. gracile_. It is slender, and delicately formed, like the prettiest gazelle.