the northern hemisphere. Thus the African Region is the more special ized division, only a small portion of the tropical element in the Indian Region, through which it is differentiated from the great Europæo Asiatic Temperate Region, being unrepresented in the African, while the African has three times as many peculiar families as the Indian.* As shown by the subjoined table, thirty of the fifty Indo-African families have a wide extralimital distribution, not less than one-fourth being emphatically cosmopolitan.

Families of Mammals represented in the Indo-African Realm, arranged to show (approxi mately) their distribution.

'The Trichechida (= Manatida) occur in Africa but not in India, but are found also in the warmer parts of America.

Wholly restricted to the Indian Region.

Rhinocerotidaæ.

Of wide extralimital range.

Mainly restricted to the Indian Region.

Found also in Intertropical America.

Chiefly African.

Summary.

Whole number

Of general distribution throughout the realm

Peculiar to the African Region...

Peculiar to the Indian Region....

Occurring in the Indian Region, but not in the African..
Of wide extralimital range

....

50

30

10

3

6

16

African Region.-The African Region, as here recognized, is nearly equivalent to Mr. Wallace's "Ethiopian Region", with the exclusion * Mr. Wallace has arrived at rather different conclusions respecting the specializa tion of the African Region, since he considers its specialization due wholly to the peculiar forms developed in Madagascar. Deducting these--for he considers Madagascar and its neighboring islands as forming a "subregion"merely of the "Palæotropical"he believes would leave, in respect to specialization, the African and Indian Regions "nearly equal". In this comparison, however, I wholly exclude the Madagascan "Lemurian" fauna, and still find Africa a considerably more specialized region.

or

of his "Lemurian Subregion". Its northern boundary will be provisionally considered as the northern mean annual of 70° F.

Asthus limited, the greater part of the Arabian Peninsula and the southern portion of the Great Sahara belong to it. But just how much of the latter belongs here, and how much to the Mediterranean Region, cannot at present be readily determined. As already noticed, it consists largely of transitional ground, and is as yet quite imperfectly known. It is to some extent, doubtless, also a barrier region; but that it is by no means an impassable obstacle is sufficiently shown by the large number of generic types of mammals that extend from the Indian Region as far southward even as the Cape of Good Hope. Even if it were an insurmountable barrier, the comparatively humid and fertile eastern coast border would afford a sufficient highway of intercommunication between Tropical Asia and Tropical Africa, and the community of life of the two regions shows that for long ages there has been this open way of interchange.

The African Region, considering its great extent and its tropical climate, is to a great degree zoölogically a unit, yet it is by no means homogeneous. At least, three subdivisions may be recognized, each of which is characterized by many peculiar genera. These subregions have already been characterized by Mr. Wallace under the names of Eastern, Western, and Scuthern. The Western (West African Province) consists of the humid, heavily wooded region of the west coast, extending to a considerable, but at present not definitely determinable, dis tance into the interior, but probably with boundaries nearly as drawn by Mr. Wallace.* The Eastern (East African Province) includes the remainder of Intertropical Africa, while to the Southern (South African Province) belongs the southern extratropical portion of the continent.

Of these divisions, the Eastern contains the greatest number of genera, as it likewise contains by far the greatest area; but it is the least specialized, only two fifteenths of its genera being peculiar to it, while of the genera of each of the other regions about one-fourth are peculiar. Nearly one-half (about forty-four per cent.) of the genera of the Eastern Prov. ince have a more or less general distribution over the whole African Region, while only a little more than a third (thirty-three to thirty-eight per cent.) of the genera of the other province have a similarly wide range. A much larger proportion of Indian génera are represented in the Eastern and Southern Provinces than in the Western. This difference is due to obvious conditions, the fertile belt of the Nile district and adjoining coast forming an easy way of intercommunication between the *The conclusions and details here presented were worked out independently and de novo by the present writer. That they agree so closely with the views and results attained by Mr. Wallace, so far as Africa south of the Great Desert is concerned, is to me a source of gratification. In order to avoid unconscious bias I purposely avoided a detailed study of Mr. Wallace's writings on this subject till my own results were written ont, and on then comparing my own conclusions with those reached by Mr. Wallace, became for the first time aware of their close agreement.

two former not equally open to the Western Province. The Eastern and Southern Provinces further resemble each other in consisting largely of grassy plains, and in being, par excellence, the land of Antelopes. On the other hand, the Western Province, in consequence of its moist climate and dense forests, is the metropolis of the African Quadrumanes, to which region no less than six genera are restricted, and where all but one are represented, while only four occur in the Eastern, and merely a few outlying species reach the Southern. Hence the Eastern and Southern Provinces are far more closely allied than is either with the Western.

Eastern Province.-The East African Province or "Subregion" includes, as claimed by Mr. Wallace, not only East Africa proper, but also a considerable portion of the Great Sahara and the whole of the northern portion of Tropical South Africa, thus bounding the Western Province on three sides. In other words, it not only includes East Africa and Southern Arabia, but all of Tropical Africa, except the western portion, situated (speaking generally) between latitude 15° north and latitude about 220 south. As is well known, it consists mainly of a moderately elevated plateau, rising, in Abyssinia, into lofty mountains. It is generally an open region, "covered with a vegetation of high grasses or thorny shrubs, with scattered trees and isolated patches of forest in favorable situations. The only parts where extensive continuous forests occur are on the eastern and western slopes of the great Abys sinian plateau, and on the Mozambique coast from Zanzibar to Sofala."* It is worthy of note that the species peculiar to the province occur almost exclusively in Mozambique, or in Abyssinia and adjoining por tions of Northeast Africa, a few extending into the Arabian Peninsula. Of the ninety genera occurring in this province, ten, which are almost cosmopolite, may be considered as having too wide a range to possess any special significance. Of the remaining eighty, about one-fourth are found also in the Indian Region, leaving three-fourths (thirty-nine) as peculiarly African. Of these, twelve only are restricted to the Eastern Province, sixteen being common to the Southern Province, and ten to the Western. The subjoined tabular list indicates approximately the distribution of the genera of the Eastern Province.

* Wallace, Geogr. Dist. Anim., vol. i, p. 259.

See Rolleston, Trans. Linn. Soc. Lond., 2d ser., Zoöl., vol. i, pp. 256, 257, 1877.

The Southern Province.-The South African Province consists of only that small portion of the continent lying south of the Southern Tropic, and is hence situated wholly within the southern warm-temperate zone. In consequence of its configuration, its limited extension, and its geographical position in relation to Intertropical Africa, it could scarcely be expected to form more than an appendage of the intertropical zone, and such it proves really to be. Its area is equal to only about one-tenth of that of the Eastern Province, yet it has eight-ninths as many genera, fully two-thirds of which are common to the two. It hence presents to only a limited degree the features of a strictly temperate fauna, and these become prominent only over the narrow belt of country south of the mountain ranges forming the northern boundary of Cape Colony and Caffraria; but here even there is a strong invasion of essentially tropical forms.

In general facies it differs little zoologically from the Eastern Province, of which it is merely a somewhat modified continuation. From its semi-temperate character it is less rich in Quadrumanes, but many other properly tropical types range nearly or quite to its southern bor

der. It has, however, about one-fourth more peculiar genera, divided about equally, and mainly between Carnivores and Rodents, four only being Antelopes, and one only (Chrysochloris) an Insectivore. Of the twenty-four genera common also to the Indian Region, one-third are Chiropters. The remaining genera are, with very few exceptions, such as occur also in the Eastern Province, only three or four being common to the Southern and Western Provinces that do not also occur in the Eastern.

Of the eighty-two genera below enumerated as occurring in the Southern Province, a considerable portion are restricted to its southern half, while many others extend only over its northern portions. A few others, while mainly restricted to this region, and eminently characteristic of it, also extend somewhat into the Eastern Province.

The Western Province.-As already stated, the Western Province differs greatly in respect to its physical characteristics from either of the other provinces of the African Region, and has, in consequence, a correspondingly specialized mammalian fanna. It resembles the Indian Region in its hot, damp climate and dense forests. And its fauna, though distinguished by many peculier genera, is also, in respect to its general facies, more like that of the Indian Region than is the fauna of any other portion of the African Region. It is similarly rich in the higher Quadrumanes and poor in Antelopes, while it shares with the