OCR Text |
Show 358 MR. R. I. POCOCK OX THE [Apr. 21, Zealand, where the most primitive type of all, Ilexathele, still survives aiwl whence the ancestor of its near ally, Scotincecus, crossed to South America. (2) South-westwards into India, Madagascar, and Tropical Africa (Ischnothele and Evagrus), whence these genera migrated into South America, passing thence into North America in later Tertiary times. (3) North-westwards into the Mediterranean Region (Phyxioschcema and Mcicrothele). (4) Northeastwards into North America, to give rise to the Mecicobothriidae. On tdie other hand, the genera of Diplurinae, which are more specialised than the Macrothelinse, 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 Mecicobothriidae, which arose in the Sonoran Region from a form, like Ilexura, allied to llexathele, themselves gave rise in early Tertiary times to the Brachybothriidae, which still exist there and have succeeded in reaching Japan (Acattyma), and to the Atypidae 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 originated 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 Mecicobothriidae moved southwards into South America, where the existing genus Mecicobothrium met the genus Scotincecius, the ancestors of which, according to my hypothesis, reached the same country by the southern route from New Zealand. The Cyrtaucheniidae of the primitive group Nemesiae 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 Reg\pn, 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 Aganippse. The explanation given above of the distribution of the Dipl urine Dipluridae applies in almost every particular to that of the Cyrtaucheniidae of the Cyrtauchenii group, except that the latter were later in the southward movement into Africa, reaching |