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Show 1897.] MR. R. I. POCOCK ON ETHIOPIAN SPIDERS. 725 species so frequently spoken of in a comprehensive sense as ' Mygale.' These belong to the suborder to which I have elsewhere applied the name Mygalomorphce, and differ from the vast majority of other spiders in possessing two pairs of lung-sacs, instead of one pair of lung-sacs and a paii of tracheal tubes, and in the circumstance that the mandibles project horizontally forwards, instead of vertically downwards, and that the fang closes almost longitudinally, instead of obliquely, backwards. The African species presenting these features appear to me to be conveniently referable to four families, each containing a considerable number of genera and each in its broad outlines easily distinguishable from the rest; though, as is tbe case in almost all the groups of this rank within the order Araneaa (Spiders), not to mention other divisions of the Animal Kingdom, genera occur in each family which more or less partake of the characters of one or more of the others and makes the task of drawing a hard-and-fast line between the groups a task of no little difficulty. This consideration has induced Mons. Simon, and following him Dr. Thorell, to look upon all the genera mentioned in this paper, as well as many others from different geographical areas, as belonging to a single family. But it appears to me that the sections here recognized as families and subfamilies have a greater value, and are more easily defined than M . Simon's families Theridiidce and Arcglopldce, and all the subfamilies of the latter, the diagnostic features of which he has not attempted to express in tabular form. The families may be recognized as follows :- a. Tarsi with only two claws on the legs, but furnished on each side of them with a dense tuft of hairs (ungual tufts). a'. The terminal segment of the posterior spinning-organs long; mandible without any apical setiform spines forming a 'rastellum' THERAPIIOSID.E. b'. The terminal segment of the posterior spinning-organs short and obtuse ; mandible usually with a set of stout spiniform setas forming a ' rastellum' BARYCIIELID E. b. Tarsi with three claws and almost always no uugual tufts. a2. Posterior spinners long and slender like those of the Theraphosidae, but longer; the anterior spinners more widely separated; lower edge of mandible with a single internal row of teeth, as in the Tkera-phosidas and Barychelida;; norastellum on mandible. DIPLURID.*:. b2. Posterior spinners shorter and thick, the anterior adjacent: mandible armed below with two rows of teeth. a3. Mandible long, projecting as in the preceding families, with the fangs closing almost straight backwards; furnished with a rastellum either in the form of setiform spines or of a spine-tipped process; thoracicfovea usually strongly procurved. (Ground Trap-door Spiders.) CTENIZID^. b3. Mandibles short, curving abruptly downwards; the fangs short, stout, and closing more obliquely inwards ; not armed with a rastellum ; thoracic fovea strongly recurved. (Tree Trap-door Spiders.) MJGIDJS. |
