396 ZOO-GEOGRAPHICAL NOTES.

tions actually take place among the fishes for spawning purposes, I was able to convince myself at the rapids of the river Rol, near Mvolo, where twice a year a movement of immense shoals of fish goes on up and down stream, an occurrence which is well known to the natives, and much desired by them, for it supplies the country far and wide with fish. I observed the fish moving down to the north at the end of October, while the contrary movement takes place, according to the statement of those who dwell there, in June.

Let us now turn our attention to another series of phenomena, which are the more interesting because they exhibit facts which seem to be opposed to the universal rules of the distribution of animals; I mean the appearance of certain species in localities where they are separated from their nearest relations by very long tracts, sometimes by whole continents.

Such cases are to be found in Europe in the presence of Cyanopica cyanea, Pall., in Siberia, whilst their nearest relations (Cyanopica Cooki) reside in Spain, of JLyogale moschata in Russia, and of MM. pyrenaica in the Pyrenees, while no species even allied to them exists in the intervening countries. An entirely similar instance is afforded by the appearance of the Angola magpie (Pitta angolensis) mm a limited district of | West Africa, while the genus Pitta most essentially belongs to Wallace’s oriental region, between which two haunts beside the ocean, lies the whole breadth of the African continent. The same holds good of Atherwra (tufted-tailed porcupine) and the West African representatives of the Tragulide ; both genera are properly oriental.

Now, as it is so difficult to account for such very exceptional cases, they must challenge us to an exact study of the intervening regions; and that surprising disclosures may often be found there is shown by the following facts:—According to my experience, Atherura is by no means rare in Central Africa, and is fairly equally distributed; in Monbuttu I succeeded in collecting within a short time a number of living specimens. In contradistinction to nonda, the common variety of porcupine (Hystrix) which is found beside it, it is called holia, and its region may at present, as far as my experience goes, be defined as extending northwards to about 3° 40’ N. lat., and