HYBACOTHE'REJM, a genus of fossil paehydermata, belonging to the division perry sodactyla, the animals of width are characterized by lowing en odd number of toes. The genus was founded by Owen on the fragmentary remains of species found in lower eocene strata; a third species from the same beds has been since described by him from more complete materials, the name pliolophusvulyieeps; he considers it only a subgenus, and as we can see no characteristics to separate it generically from the other two, we place it here as a true hyracothere. The fossil was discovered in a nodule from the Roman cement bed of the London clay near Harwich. It is the most complete cocene mammalian fossil of the London clay. It consists of an entire skull and a por tion of the rest of the skeleton, including the right humerus and femur, a great part of the left femur, the left tibia, and three metatarsal bones, apparently of the same foot, besides fragments of pelvis, ribs, and vertebra. The bead is 5 in. long, and 2 in. 2 lines broad; it is slender, tapering gradually from the zygomatic region to the muzzle; the upper outline is straight; the bony rim of the orbit is incomplete behind for about one fifth of its circumference. The narrow skull and incomplete orbit ally it to the paleo there; the same form of orbit occurs also in the rhinoceros, and more exactly in the tapir. The straight contour of the skull, and the structure of the nasal aperture, show affinities with the horse and hyrax. The third molar of the upper jaw shows the struc ture of the teeth. The teeth, as well as the form of the lower jaw, tell plainly of the
herbivorous character of the hyracothere. The bones of the leg exhibit affini ties, and their form and proportions are betWeen those of the hyrax and thAapir. The second species was founded on a mutilated cranium, rather larger than a hare's, found in the cliffs of London clay near Herne bay. It shows a skull very like the first species, though broader at the orbital region. The third molar tooth has a larger number of cones than the same tooth in the first species. The third species was founded on several teeth which belonged to a smaller animal than either of the others, found in the eocene sand underlying the Red Crag at Kyson, in Suffolk. The molar exhibits a structure similar to that of the others. From the same deposit were obtained two teeth belonging to a lower jaw, one of them, the third molar, still in its socket, and having a fragment of the jaw attached to it. These teeth were considered by Owen to belong to a quad rumanous animal, and were described by him as maeacus eocanus, once the first terrestrial mammal which has been found in the London clay, and the first quadruman ons animal hitherto discovered in any country in tertiary strata so old as the eocene period." Since its publication, speculative geologists have made good service of this monkey." Owen has, however, since stated (Ann. Kat. Hist., Sept., 1802), that the teeth belong to time third species of hyracothere,