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Show 1 9 0 3 . ] GEOGRAPHICAL DISTRIBUTION OF SPIDERS. 3 5 3 Mauritius ; Sasonichus, S. India; Sipalolasma and Plagio-bothrus, Ceylon; Encyocrypta, Singapore to Australia; Barychelus, New Caledonia; Idioctis, Upolu ; Idiommata and Trittame, Australia ; Psalistops, Sto this, Euthyccnlus, Epipedesis, Cosmopelma, Trichopelma, ? Acanthogonalus, Homceoplacis, Idiophthalina, Strophceus, Cyrtogrammomma, Neotropical Region. ft. Diplothelse : Diplothele, India and Ceylon ; Forsythula, Madagascar. c. Sasones : Sason, Seychelles, Maldives, Ceylon, India, and Celebes ; ? Bianus, Pinang. The existence of a primitive type, Leptopelma, in the Mediterranean area, and the entire absence of the group from the Sonoran Region and from China, suggest its origin in the western part of the Old World. Moreover, the presence of genera in Sokotra, Mauritius, Madagascar, and all over the Ethiopian Region attests a southern migration at a very early date. Similarly, the extension of the group over the Oriental Region, from India to Australia, suggests a perhaps contemporaneous movement in a south-easterly direction over the area in question, after the isolation of New Zealand. Again, the absence of genera of this family from the Sonoran Region, coupled with the relationship between the Mediterranean genus Leptopelma and many of the Neotropical types on the one hand, and between the remainder of the latter and the Tropical African genera on the other, points to a transatlantic connection between Africa and Europe and South America. At the same time, the possibility of a migration into South America from Australia across the area of the Pacific must be borne in mind. In the absence of evidence to the contrary, the genus Sason, specialised both in structure and habits, may be regarded as having arisen from a primitive type in the area it at present occupies. That this must have taken place in very early times, before the severance of the Seychelles from India and Ceylon, would be an unavoidable conclusion, were we sure of the distinctness of the Seychellesian from the Ceylonese species. But the occurrence of one of the Ceylonese species in the Maldives proves, I think, artificial introduction into that Archipelago ; and the same explanation may apply to the presence of the genus in the Seychelles. One other point of interest remains, and that is the unquestionably close relationship that obtains between the Indian and Ceylonese genus Diplothele and the Mascarene Forsythida, the latter being a more specialised type. This is almost the only undoubted case of similarity between the faunas of Madagascar and India that the Mygalomorphae supply. Family A v ic u l a r it d .e . The distribution of this family is most instructive. The heterogeneous group of genera associated together as 23* |