OSTEOLOGY OF THE HYOPOTAMIDH:. 
21 
of its osteology, and, comparing it with some of the living Paridigitates, found that it 
and they possess many features in common. The naturalists Avho have ventured to 
theorize during the period of purely descriptive science which lies between the time of 
Cuvier and the complete revolution caused by Darwin’s great work, looked always at 
the accurate and talented description of Cuvier, finding no good materials in the works 
of modern palaeontologists from which to draw their means of generalization. As this 
absence of detailed descriptions of fossil European Mammalia was prolonged till our 
own time, we can understand how, even after the great revolution caused by the publi- 
cation of Darwin’s views, all writers that were leading the new movement of evolution, 
and trying to apply the theory of descent to our modern Paridigitata, had still to consult 
the works of Cuvier to find full and accurate information. There they could find only 
Anoplotherium fully described (as the Xiphodon and, especially, Dichobune were very much 
neglected in the ‘ Ossemens Fossiles’) ; and as it was, moreover, the most ancient form 
known, they placed it at the commencement of their pedigrees of Paridigitata. But if 
we consider the structure of the feet in Anoplotherium , we cannot avoid the conclusion 
that this genus is only an exceedingly reduced form, descended from some earlier 
Ungulate of the early Tertiary or, more probably, Cretaceous period. Anoplotherium is 
clearly the last remnant of a dying-out branch, in no case the progenitor of the wonder- 
fully rich and diversified Paridigitata which succeeded it in the Miocene period, and 
which became so enormously developed in the Upper Miocene and Pliocene epochs, form- 
ing in our own time perhaps one of the most richly developed of animal groups. The 
feet of Anoplotherium are so much reduced, presenting only two developed meta- 
carpals and metatarsals, with merely rudiments of the lateral toes, which certainly existed 
in its ancestors, that we cannot imagine such a reduced form giving rise to Miocene or 
even modern Paridigitata, many of which have four completely developed metacarpals 
and metatarsals. Besides, it is a very general truth that only those families which 
were exuberantly developed in bygone times, presenting many subgenera and a great 
variety of specific forms of different size, have had any chance of leaving a progeny 
behind them. We see examples of this in some of our recent genera the pedigree 
of which is now very completely known. There can be, in my opinion, no reasonable 
doubt that the Horse descended from the P 'aim 'other ium (very probably the Rhinoceros 
had the same origin from a Pakeotheroid form, though this is not so certain) ; and see 
what immense diversity we find in the Polmotheridm of the Eocene and Miocene epochs. 
The quantity of described species of Paloeotherium is only a small fraction of the 
quantity that really existed, as every one who looks through a large collection of 
Eocene teeth becomes aware. Besides, the PalceotJieridce range in size from P. mini- 
mum (known only by its metapodium), not larger than a rabbit, through all inter- 
mediate sizes to P. magnum , fully as large as our Rhinoceros. We may mention that 
the Paloplotherium and Anchilophus belonged also to this group, and are extensively 
developed in the Eocene epoch. Only such prolific types, sending branches in all direc- 
tions, have any chance of not wholly dying out in the course of time. If, in the struggle 
