308 MR. R. I. POCOCK ON THE [ Apr. 21, 
Zealand, where the most primitive type of all, Hexathele, still sur- 
vives amd whence the ancestor of its near ally, Scotinecus, crossed 
to South America, (2) South-westwards into India, Madagascar, 
and Tropical Africa (fschnothele and Hvagrus), whence these 
genera migrated into South America, passing thence into North 
America in later Tertiary times. (3) North-westwards into the 
Mediterranean Region (Phyxioschema and Macrothele). (4) North- 
eastwards into North America, to give rise to the Mecicobothriide. 
On the other hand, the genera of Diplurine, which are more 
specialised than the Macrotheline, and therefore of later origin, 
were represented in Tertiary times by genera (Brachythele) both 
in the Sonoran and Mediterranean Regions. From the latter, 
perhaps in the Oligocene era, they descended into Africa and 
Madagascar, but do not appear to have entered the Oriental 
Region at all. From Africa and Madagascar they probably 
entered South America, and perhaps Australia also, though they 
may equally well have passed from South America to Australia. 
In later Tertiary times also it is probable that there was a 
commingling of Sonoran and Neotropical forms due to southward 
and northward migration. 
The Mecicobothriide, which arose in the Sonoran Region from 
a form, like Hexura, allied to Heaathele, themselves gave rise in 
early Tertiary times to the Brachybothriide, which still exist 
there and have succeeded in reaching Japan (Acattyma), and to 
the Atypidee as well, which also crossed into Eastern Asia, and 
thence extended westwards as far as Ireland and Algeria, and 
southwards into Burma and Java. In South-eastern Asia from a 
primitive Atypoid genus origimated Calommata, which probably in 
the Pliocene extended right away from the Oriental Region into 
West Africa, the existing species being known only from the 
latter area and from Indo-Malaysia and Japan. 
In later Tertiary times the Sonoran Mecicobothriide moved 
southwards into South America, where the existing genus 
Mecicobothrium met the genus Scotinecus, the ancestors of which, 
according to my hypothesis, reached the same country by the 
southern route from New Zealand. 
The Cyrtaucheniide of the primitive group Nemesize at an 
early date entered India, Africa, and Madagascar from the north, 
or equally likely originated in Africa itself and spread thence 
into the Mediterranean Region, into Madagascar and India, into 
South America and into the Australian Region, as is attested 
by the closeness of the similarity between the South-African, 
South-American, and Australian species, and the absence of the 
group from the eastern parts of the Oriental and from the Sonoran 
Regions. Within Australia itself they seem to have given rise 
to the group Aganippe. 
The explanation given above of the distribution of the 
Diplurine Dipluride applies in almost every particular to that of 
the Cyrtaucheniidee of the Cyrtauchenii group, except that the 
latter were later in the southward movement into Africa, reaching 
