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demonstrate, so far as present evidence goes, that the mastodons originated in north-eastern Africa.

There is, however, another strange ungulate from the Fayum Eocene which is of not less importance from the present point of view. To this strange monster its discoverer (who was of opinion that it was related to the rhinoceroses) has given the name Arsinoetherium, derived from the goddess Arsinöe. The skull of this animal, which measures approximately a yard in length, is characterised by the presence of a huge pair of horns

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FIG. 4.-DENTITION OF MERITHERIUM LYONSI.

i, incisors; c, canine; pm, premolars; m, molars.

on the nose, followed by a rudimentary pair at the hinder end of their bases (fig. 5). To support the weight of these great horns the nasal region of the skull is connected by a bridge of bone with the front of the upper jaw. An important feature of the genus is the uniform series formed by the teeth, which show no gaps, and have the canines no taller than the rest of the series, thus not forming tusks. This feature, it may be observed, is a specialised one, which may perhaps be accounted for by the heavy armament of horns rendering tusks unnecessary.

The osteology of the rest of the skeleton of this monster is not yet fully worked out, but it is quite likely that the genus will eventually prove to be distantly related to the Proboscidea, and more intimately to the

primitive Eocene group of ungulates known as Amblypoda, of which the typical genus Coryphodon is common

[graphic]

FIG. 5. SKULL OF ARSINOETHERIUM ZITTELI (length, 3 feet).
(This and fig. 1 are reproduced, by permission, from the Guide to the
Natural History Museum.)

to the lower Eocene of Europe and North America, while the more specialised Uintatheres (frequently known as Dinocerata) are restricted to the upper Eocene of the latter continent. Although the Uintatheres have long horn-like protuberances on the skull, they retain tusklike canines, while these teeth are also well developed in Coryphodon. Evidently, then, both groups are more generalised than Arsinoetherium, to which the latter may

*I am indebted to Dr Andrews for this information.

be ancestral. It may be added that the Amblypoda resemble the Proboscidea in having the bones of the different segments of the limbs placed almost vertically one above the other.

This cursory review of the mammals of Ethiopian Africa may be brought to a close by a brief reference to the strange creatures properly denominated aard-varks, but often termed by sportsmen and travellers ant-bears. Although utterly unlike any other living mammals, it is generally considered that these strange animals may be related to the equally remarkable pangolins or scaly ant-eaters, of which some are African and the rest Asiatic. Whether the presumed affinity of both these creatures to the edentates of South America is founded on fact, is more than doubtful. Aard-varks are found in fossil form in the Pliocene of Samos and Persia; and ancestral types of the same group are said to occur in the middle Tertiaries of France. More remarkable still is the occurrence of an extinct generic type of aard-vark in the superficial deposits of Madagascar. For, although we have not yet had occasion to allude to the fact, the mammalian fauna of that island is totally distinct from that of Africa, consisting chiefly of peculiar types of lemurs, Insectivora, rodents, and mungoose-like Carnivora, together with the somewhat civet-like, and yet altogether peculiar, fossa (Cryptoprocta). With the exception of two small kinds of hippopotamus, now extinct, and a bush-pig, both of which may have reached the island by swimming from the mainland, Madagascar possesses none of the large African mammals-a fact which may be taken as indicative of the great length of time during which it has been isolated. This being so, the occurrence of fossil aard-varks in Madagascar proves these animals to be very ancient inhabitants of Africa.

It may be added that this remarkable distinctness of the mammalian fauna of Madagascar from that of the mainland induced Mr Blanford to regard that island as representing a zoological province apart from the Ethiopian region, in which it had previously been included. I feel convinced that this is the right way of looking at the matter, in spite of the fact that, in a paper on the distribution of certain groups of spiders, Mr R. I. Pocock has seen reason to revert to the older view.

We are now in a position to discuss the bearings of the foregoing facts on the past history of the mammalian fauna of Ethiopian Africa.

Writing so long ago as 1868, when the information on the subject was far more incomplete than is now the case, Mr Huxley, in the paper standing first in our list, made the following remarkable statement :

"The existence of these western annectent groups, now in many cases confined to the southern parts of the New and Old Worlds, and separated by thousands of miles of sea, is utterly unintelligible and inexplicable without the aid of paleontology, which demonstrates that, in the earlier part of the tertiary epoch, western and northern Arctogæa, from Nebraska through central Europe to the Siwalik Hills, was inhabited by a fauna which, so far as mammals are concerned, was competent to supply Africa and India with their apes, their Ungulata, their Carnivora, and to furnish AustroColumbia [South and Central America] with the Proboscidea, horses, and Machairodus, which it once possessed, and with its existing Tapirs and Cameline and Marsupial quadrupeds.'

The same author subsequently took into consideration the possibility that certain types of birds, now mainly characteristic of the southern hemisphere, might have had a southern origin. He concluded, however, as

follows:

"The distribution of Psittacula, for instance, is quite unintelligible to me upon any other supposition than that this genus existed in the miocene epoch, or earlier, in Northern Arctogæa, and has thence spread into Austro-Columbia, South Africa, India, and the Papuan islands, where it is now found.'

This theory of the immigration-or 'radiation,' as it is now the fashion to call it-of northern forms into Africa during the Pliocene epoch was more fully developed by Mr A. R. Wallace, and in this shape was accepted by Mr W. T. Blanford in the address referred to above. Briefly stated, this hypothesis is as follows. During the whole of the latter portion of the Tertiary epoch the Sahara desert (not, as once supposed, in the form of a sea) formed an effectual barrier to the migration of the great majority of terrestrial mammals between Ethiopian and northern Africa, the latter of which

appears at this time to have been connected by land with Europe. At a comparatively early, although unknown, date in the Tertiary period the ancestors of the existing mammalian fauna of Madagascar, such as lemurs, Insectivora, civet-like creatures, the fossa, and, I may add, aardvarks, effected an entrance from the north, probably along the eastern side of the continent, into Ethiopia, which was at that time united with the great island on the east coast. At a later date Madagascar, which may also at the same epoch have been in connexion with India by way of the Comoro and Seychelle islands, became insulated, and was thus prevented from receiving any of the subsequent Pliocene immigrants into Ethiopia, with the exception of a bush-pig and two hippopotami, which, as already mentioned, may have reached the island by swimming across the intervening channel.

During the second, or Pliocene, invasion of Ethiopia from the northward, all or, at any rate, most of the more specialised and larger types of mammals, such as apes and monkeys,* giraffes, okapis, and antelopes, wart-hogs, bush-pigs, and hippopotami, zebras, asses, and rhinoceroses, elephants and hyraces, together with ostriches, obtained for the first time an entry into the central and southern districts of the great continent. Finding the country unoccupied by large animals of their own type, and at the same time eminently suited to their own special requirements, the strangers rapidly developed in their new home to an almost unprecedented extent, with the result that, in the course of ages, there arose the wonderful Ethiopian mammal fauna as it was presented to us in the early days of European exploration and sport in the Dark Continent. Many new generic types of large mammals were, indeed, probably evolved de novo in the Ethiopian area, although a large proportion of those now found there were originally represented in their presumed ancestral northern home, where a large percentage of what we now rightly regard as exclusively Ethiopian types appears to have soon afterwards died out. Several of these existing genera are, as already indicated, represented in the Pliocene of Greece, but others seem

The recent discovery in Madagascar of an animal apparently intermediate between lemurs and monkeys presents a certain difficulty with regard to the date of immigration of the latter group.

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