352 MR. R. I. POCOCK 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 Zdiops reached South America, it is probable that 
Pseudidiops, a specialised offshoot of that genus, arose within the 
Neotropical Region. 
Family HaLonoprocrip#. 
The three known genera of this family, a specialised offshoot of 
the Ctenizide, namely, Halonoproctus from China, Chorizops and 
Cyclocosmia from the Sonoran Region, also constitute a northern 
group, which has not migrated into the southern continents. 
Family AcTINOPODIDA. 
Of the two genera of this family, Hriodon (Missulena) 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 Cyrtaucheniidee 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 Micip#. 
The Migidee are essentially a southern group. Two or three 
genera (Myrtale and Thyropeus) occur in Madagascar; Moggridgea 
in Sokotra, Nyasaland, Natal, and Cape Colony ; Heteromigas in 
Tasmania; J/igas, 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 Cyrtaucheniide of the section Nemesie, an 
ancient and very widely distributed group, with representatives 
in South Africa, Madagascar, South America, Australia, and 
New Zealand, the countries to which the Migid 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. s 
Family BARYCHELIDA. 
The genera of this family fall into three sections, which may be 
arranged in order of specialisation as follows :— 
a. Barycheli: Leptopelma, Mediterranean Region ; A trophothele, 
Sokotra; Hubrachythele,Somaliland; Cyphonisia, W. Africa; 
Pisenor, hi, Africa; Brachionopus, Cape Colony ; Tigidia, 
