XX 
INTRODUCTTOX. 
fn.uiia, nltlioi]<fli tlicrc is miicli to be said for tiic o])posi(c view. The Anthracotlieriiilae 
are represented in tlie almost conteir])orary deposits of Egerkingen by tlie genera 
Ancodon and Bhagatherivm, ]n?<t as in the Eayuin, and, moreover, in both places they 
are accompanied by (Ireodonts belonging to the Hyienodontidae ; but while the 
(h’codonts occur iu the earlier beds of Europe, this does not seem to be the case with 
the Anthracotheres, so that here there may be a trace of an interchange of forms 
jtossihly towards the end of the Middle Eocene, the Creodonts having passed into 
Africa at the same time as the Anthracotheres migrated north. Professor Osborn 
has already suggested that such a migration took place about tins time, in order to 
account for the appearance in the Upper Eocene of Europe of forms like certain 
highly specialised Knminants, the Anomalures, and perhaps some Edentates. The 
Anthracotheres persisted in Africa at least till the Power Miocene, at wliich horizon 
they are represented by Brachjjodus africainis, and it is, pointed out below that these 
animals in many points, e.(j. in the pelvis (see p. 185), approach very nearly 
to the Ilippopotamidie, which are probably derived from them. Remains of one 
of the earliest and most primitive Hippopotami known, viz. 11. hipponotsis, have 
already been found in the Middle Pliocene of Egypt, so that there is every })ros[)ect 
that annectant forms between Hippopotamus and the Anthracotheres may be discovered 
in this region in deposits between the Lower Pliocene and the Pliocene. 
d'he peculiar genus Geniolipus is perhaps the earliest-known member of the 
Suidae, but although the lower cheek-teeth seem to be undoubtedly those of 
a primitive Pig, the great enlargement of the anterior . pair of incisors and the 
reduction of the posterior incisors and canines are quite different from what is usually 
found in members of this family. Geniohijus, in fact, may be regarded as an early 
specialised form of a group of nliich the generalised members have still to be found ; 
they probably inliabited Africa and passed north, ])erhaps in the Middle Eocene 
migratioir referred to above. The occurrence of the peculiar ventral process arising 
from the sympliysial region of the mandible suggests some possible relationship n ith 
the ElotheriicUe of the Miocene of Europe aird America, a gron[) in which somewhat 
similar processes occur ; but, if only on account of the peculiarities of its anterior teeth, 
it seems impossible that Geniohpus can at most be more than an early ofti^hoot of the 
ancestral stock of that group. 
In the Fayfinr the Sirenia are represented by one genus, Eosiren, only, but in the 
earlier and more exclusively marine beds of the Mokattam Hills, near Cairo, other 
more primitive types occur, the skull of one of which, Eotturium, is described below 
