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Show 352 MR. R. I. TOCOCK ON THE [Apr. 21, its absence at the present time from this region, as well as from the West Indies and Central America. These considerations justify the view that South America acquired this element in its fauna, not from North America but from Africa. But by whatever route Idiops reached South America, it is probable that Pseudidiops, a specialised offshoot of that genus, arose within the Neotropical Region. Family H a l o n o p r o c t im . The three known genera of this family, a specialised offshoot of the Ctenizidse, namely, IIalonoproctus from China, Ghorizops and Cyclocosmia from the Sonoran Region, also constitute a northern group, which has not migrated into the southern continents. Family A c tinopodid^e . Of the two genera of this family, Eriodon (Missidena) is restricted to Australia, and Actinopus to the Neotropical Region. The descent of this family is doubtful, but its structure and distribution suggest its origin in the Southern hemisphere from the Cyrtaucheniidse of the group Aporoptychi, which exist in South America and South Africa. Its present distribution may be accounted for on the hypothesis of the migration of the ancestral form either from Africa to Australia and thence to South America, or the other way about. Family M ig id ^e . The Migidse are essentially a southern group. Two or three genera (Myrtale and Thyropceus) occur in Madagascar; Moggridgea in Sokotra, Nyasaland, Natal, and Cape Colony ; Heteromigas in Tasmania; Migas, nearly related to Moggridgea, in New Zealand ; and an undescribed genus, close to Heteromigas, in Chili. The recurvature of the thoracic fovea in this family suggests its descent from Cyrtaucheniidse of the section Nemesia?, an ancient and very widely distributed group, with representatives in South Africa, Madagascar, South America, Australia, and New Zealand, the countries to which the Migidae are now restricted. The distribution of the latter attests not only a southern origin, perhaps in the Afro-Mascarene area, but also migration thence to Australia and New Zealand, and from Australia to South America. Family B a r y c h e l id .e . The genera of this family fall into three sections, which may be arranged in order of specialisation as follows :- a. Barycheli: Leptopelma, Mediterranean Region; Atrophothele, Sokotra; Eubrachythele, Somaliland; Cyphonisia,W. Africa * Pisenor, E. Africa; Brachionopus, Cape Colony; Tigidia, |
