INTRODUCTION. 
XV 
many of these (e. g. ArcJia’oIi>/ras) do not seem to differ in any important 
particulars from some of the smaller Typotheria, others of the more primitive 
forms belonging to Ameghino’s family, the Acoelodidae, may perhaps approach the 
ancestral forms from which the Ilyracoidea originated. 
Although Arsinoitherium is certainly the most extraordinary of the Ungulates 
found in these beds, nevertheless tlie remains of the primitive members of the 
Proboscidea are perhaps of greater scientific interest, because they help to fill, 
at least to a large extent, one of the most obvious gaps in our knowledge of 
the extinct Mammalia. Previous to their discovery the earliest Proboscideans 
known were from the Lowmr Miocene (Burdigalien) of Europe and Northern 
Africa, and although many earlier deposits rich in mammalian remains were known 
in various parts of the world, in none of them was any trace of Proboscidea found, 
so that their appearance in Europe at the beginning of the Miocene period 
must be the result of their immigration from other regions. The probability that 
Africa would be found to be the original home of these animals was pointed out 
by several writers, notably by Osborn, Stehlin, and Tullberg. The first of these * 
suggested that probably not only the Proboscidea but also the “ Hyracoidea, certain 
Edentates, the Antelopes, the Giraffes, the Hippopotami, the most specialised Ruminants, 
and among the Rodents the Anomalures, Dormice, and Jerboas, among Monkeys 
the Baboons,” and, as his map suggests, the Sirenia also, originated in this region. 
Osborn also put forward the theory that a succession of migrations from Africa 
to Europe occurred, notably at the end of the Eocene, at the beginning of the 
Miocene, and again in the earliest Pliocene. It was in the early Miocene migration 
that the Proboscidea passed out of Africa for the first time so far as known. 
Stehlin f, who also emphasized the importance of Africa as a probable centre of 
mammalian evolution, expressed much the same views. Tullberg J likewise regarded 
Africa as a centre of mammalian radiation, and pointed to Ilystrix (or the nhole 
of the Hystricognathi), the Simioe (Anthropoidea), and the Proboscidea as having 
probably migrated thence in the early Miocene. It is therefore very satisfactory 
* “ Correlation between Tertiary Mammal Horizons of Europe and America,” Ann. N. T. Acad. Sci. 
vol. xiii. (1900) pp. 1-72. 
t “Ueber die Geschiclite des Suiden-Gebisses, Pt. II.,” Abhandl. d. Schweiz. Palaeont. Gesellsch. 
vol. xxvii. (1900) p. 477 et seq. 
J “Ueber das System der Nagetiere,” Nov. Act. E. Soc. Sci. Upsala, [3] vol. xviii. (1899) p. 483. Also 
for the general question of mammalian distribution, see Lydekker, Geograpliical Hislory of Mammals 
^ 1890). 
c2 
