(_e_) The _Afro-Arabian Province_ includes Abyssinia, with S. Arabia, the African shores of the Gulf of Aden, and Socotra. The province contains a singular mixture of types. The high ground of Abyssinia stands like a lofty European island in the midst of a tropical plain, with Palaearctic genera flourishing like hardy northern plants on a mountain in low latitudes. _Helix_, _Vitrina_, and _Pupa_ abound, with a few _Clausilia_ and even a _Limax_. On the lower levels occur _Limicolaria_ (3 sp.), _Subulina_ (7 sp.), _Helicarion_, and _Homorus_, but land operculates are entirely wanting. Characteristic of the province as a whole are various forms of _Buliminus_, which in Socotra are represented by two peculiar sub-genera, _Achatinelloides_ and _Passamaiella_. In S. Arabia the mixture of types produces curious results: the _Helix_, _Clausilia_, and _Vitrina_ being Palaearctic, the _Limicolaria_ and all the operculates Ethiopian, while the single _Trochomorpha_ is Indian. Indian influence, indeed, comes out unmistakably throughout the province. Thus in Socotra there are two _Cyclotopsis_, in Abyssinia two _Africarion_ (closely related to the Indian _Girasia_), two _Microcystis_, and a _Glessula_, and in the Scioa district there is a _Sitala_. The fresh-water Mollusca of Socotra are Indian forms. [Illustration: FIG. 219.--_Tiphobia Horei_ E. A. Smith, L. Tanganyika.] [Illustration: FIG. 220.--Mollusca characteristic of L. Tanganyika: =A=, _Nassopsis nassa_ Woodw.; =B=, _Spekia zonata_ Woodw.; =C=, _Syrnolopsis lacustris_ E. A. Smith.] [Illustration: FIG. 221.--_Achatina zebra_ Lam., S. Africa. × ½.] (2) =The South African Sub-region.=--The principal characteristic of the Mollusca of S. Africa is the occurrence of numerous small species of Helicidae, belonging chiefly to the groups _Pella_, _Phasis_, _Dorcasia_, and _Sculptaria_, all of which are practically peculiar. Carnivorous genera are also prominent, _Ennea_ here attaining its maximum. _Rhytida_ (to which several species still regarded as _Pella_ belong) is common only to the S. Pacific and Australasia, and forms, with _Isidora_ among the fresh-water pulmonates, a remarkable link of connexion. _Aerope_, the largest of all helicoid carnivorous genera, and _Chlamydephorus_, a carnivorous slug with an internal shell, are peculiar. _Achatina_ is still abundant, but _Limicolaria_ is wanting. _Livinhacea_, a form with a continuous peristome, perhaps akin to _Bulimus_; _Apera_, a form of slug; and _Coeliaxis_, a genus perhaps akin to the Papuan and Queensland _Perrieria_, are all peculiar. The land operculates, which are not numerous, are of the East African type. _Land Mollusca of the S. African Sub-region_