After much search, however, I think that such a case is to be made out in favour of the pedigree of the Horses.
The genus Equus is represented as far back as the latter part of the Miocene epoch; but in deposits belonging to the middle of that epoch its place is taken by two other genera, Hipparion and Anchitherium[1]; and in the lowest Miocene and upper Eocene only the last genus occurs. A species of Anchitherium was referred by Cuvier to the Palæotheria under the name of P. aurelianense. The grinding-teeth are in fact very similar in shape and in pattern, and in the absence of any thick layer of cement, to those of some species of Palæotheriurn, especially Cuvier's Palæotherium minus, which has been formed into a separate genus, Plagiolophus, by Pomel. But in the fact that there are only six full-sized grinders in the lower jaw, the first premolar being very small, that the anterior grinders are as large as or rather larger than the posterior ones, that the second premolar has an anterior prolongation, and that the posterior molar of the lower jaw has, as Cuvier pointed out, a posterior lobe of much smaller size and different form, the dentition of Anchitherium departs from the type of the Palæotherium, and approaches that of the Horse.
Again, the skeleton of Anchitherium is extremely equine. M. Christol goes so far as to say that the description of the bones of the horse, or the ass, current in veterinary works, would fit those of Anchitherium. And, in a general way, this may be true enough; but there are some most important differences, which, indeed, are justly indicated by the same careful observer. Thus the ulna is complete throughout, and its shaft is not a mere rudiment, fused into one bone with the radius. There are three toes, one large in the middle and one small on each side. The femur is quite like that of a horse, and has the characteristic fossa above the external condyle. In the British Museum there is a most instructive specimen of the leg-bones, showing that the fibula was represented by the external malleolus and by a flat tongue of bone, which extends up from it on the outer side of the tibia, and is closely anchylosed with the latter bone[2]. The hind toes are three, like those of the fore leg; and the middle metatarsal bone is much less compressed from side to side than that of the horse.
In the Hipparion the teeth nearly resemble those of the Horses, though the crowns of the grinders are not so long; like those of the
- ↑ Hermann von Meyer gave the name of Anchitherium to A. Ezquerræ; and in his paper on the subject he takes great pains to distinguish the latter as the type of a new genus, from Cuvier's Palæotherium d' Orleans. But it is precisely the Palæotherium d' Orleans which is the type of Christol's genus Hipparitherium; and thus, though Hipparitherium is of later date than Anchitherium, it seemed to me to have a sort of equitable right to recognition when this address was written. On the whole, however, it seems most convenient to adopt Anchitherium.
- ↑ I am indebted to Mr. Gervais for a specimen which indicates that the fibula was complete, at any rate in some cases; and for a very interesting ramus of a mandible, which shows that, as in the Palæotheria, the hindermost milk-molar of the lower jaw was devoid of the posterior lobe which exists in the hindermost true molar.
