OCR Text |
Show 350 MR. R. I. POCOCK ON TliE [Apr. 21, within the limits of the Mygalomorphae. This conclusion as to theii* descent is supported by the fact that the specialised arrangement of the eyes is foreshadowed in Dyarcyops, one of the Nemesiae, and by the presence of a single row of ungual pectinations in the Aganippae and all the Australian Nemesiae, two such rows being characteristic at least of the southern forms of the Cyrt-auchenii. The Aporoptychi are specialised Cyrtauchenii. Their distribution suggests that they originated in South America or South Africa, and crossed from the one continent to the other when the two were united. This conclusion is strongly supported by the occurrence of two of the genera in both of the areas in question. Family Ctenizid^e. The genera of the subfamily Ctenizinae are almost exclusively northern. Cteniza, JEpycephalus, and Cyrtocarenum are restricted to the Mediterranean; Sterrhochrotus occurs in Turkestan; Latouchia in China and the Himalayas; Pachylomerus in Spain, Algeria, Japan, N., Central, and S. America, and the West Indies; Bothriocyrtum in California; Conothele ranges from Burma to the Solomon Islands. The only genus which is exclusively southern is Stcisimopus, which is confined to S. Africa. The structural features of this group suggest that it is a specialised offshoot from some northern forms of the Cyrtau-cheniidse. This conclusion is borne out by the more restricted distribution of the genera, which, in virtue of their later appearance in the Northern hemisphere, have had less time to distribute themselves over the southern continents. The only genus which has entered the Ethiopian Region, namely Stcisimopus, appears to have done so not earlier than the Pliocene, since it is seemingly not represented in Madagascar. Conothele, too, seems to have migrated southwards by way of Burma to the Solomon Islands, after the separation of Australia; Pachylomerus, the only form which enters the Neotropical Region, appears almost certainly to be a northern immigrant from the Sonoran region. The Idiopine section, apparently a specialised offshoot of the Ctenizinae, has, on the contrary, a more southern distribution than the typical Ctenizinae. The genus Idiops (Acanthodon) itself has representatives in Central Asia, Syria, Arabia, India and Burma, Tropical and South Africa, and S. America ; Heligmomerus occurs in India, Ceylon, and Tropical Africa; Gorgyrella in S. Africa; while the aberrant Pseudidiops is confined to the forests of South America. The presence of the genus Idiops so far north as Central Asia and Syria, and in India, Burma, Tropical and Southern Africa, and Brazil, attesting as it does considerable powers of adaptation to varied climatic and other physical conditions, justifies the supposition that the genus never formed part of the Sonoran fauna of America. Otherwise it would be difficult to account for |