XX 
INTRODUCTION. 
(anna, al(lion<4'li (liore is mncli to bo said for tlic opposite view. Tlie Antliracotlicriidsc 
arc roj)rc\S('ntod in tlie almost €ontem])ornry deposits of Egerkingen by tlie genera 
AucodoT) and liliagafJieyivm, jnst as in the Eaynm, and, moreover, in both places they 
are accomjianied by (Ireodonts belonging to the llymnodontidcC ; bnt while the 
Creodonts ocenr in the earlier beds of Europe, this does not seem to be the case with 
the Anthracothercs, so that here there may be a trace of an interchange of forms 
jiossibly towards the end of the iMiddle Eocene, the Creodonts having passed into 
Africa at the same time as the Anthracothercs migrated north. Professor Osborn 
has already suggested that such a migration took place about this time, in order to 
account for the appearance in the Upper Eocene of Europe of forms like certain 
highly specialised lluminants, the Anomalures, and perhaps some Edentates. The 
Anthracotheres persisted in Africa at least till the Lower Miocene, at which horizon 
they are represented by Bracliijodus africamis, and it is pointed out below that these 
animals in many points, e.g. in the pelvis (see p. 185), approach very nearly 
to the Ilippopotamida?, which are probably derived from them. Remains of one 
of the earliest and most primitive Tlippopotami known, viz. II. hipponensis, have 
already been found in the Middle Pliocene of Egypt, so that there is every prospect 
that annectant forms between Hippopotamus and the Anthracotheres may be discovered 
in this region in deposits between the Lower Miocene and the Pliocene. 
d'he peculiar genus Geiiiolvjus is perhaps the earliest-known member of the 
Suidm, 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. Geniohjus, in fact, may be regarded as an early 
specialised form of a group of \\hich the generalised members have still to be found ; 
they probal)ly inliabited Africa and passed north, perliaps in the Middle Eocene 
migration referred to above. The occurrence of the peculiar ventral process arising 
from the sympbysial region of the mandible suggests some possible relationship with 
the Elotheriid.c of the Miocene of Europe and America, a group in which somewhat 
similar processes occur ; but, if only on account of the peculiarities of its anterior teeth, 
it seems impossible that Geniolnjus can at most be more than an early offshoot of the 
ancestral stock of that group. 
In the Fayrfni the Sirenia are represented by one genus, Eosiirn, only, but in the 
earlier and more exclusively marine beds of tlie Mokattam Hills, near Cairo, other 
more primitive types occur, the skull of one of which, Hutltm' ttiii, is described below 
