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Show i S/O.J REV. O. P. CAMBRIDGE ON THE GENUS IDIOPS. 103 Labium small, oblong, rather narrower at the apex than at the base. Legs strong, variously armed with spines, and terminating with three claws, the two superior ones of which are sometimes pectinated. Palpi long, strong, and armed with spines ; in the female sex pedi-form, and ending with a simple curved claw; in the males terminating with palpal organs, which in general structure resemble closely those of the male sex in all known species of the Mygalides, viz. a corneous bulb slightly attached to the underside of the digital joint, and prolonged into a variously formed, but generally simple, spinous projection. M . Guerin remarks that nothing is known of the habits of his species I. petitii; the striking similarity, however, in one portion of its structure (viz. the strong and peculiar spines on the palpi, legs, and falces) seemed to indicate a habit similar to that of Cteniza, Latr., Atypus(ha.tv.), and Actinopus (Perty), i. e. the formation of a tubular silken domicile in a hole dug out of the earth, and closed probably by a hinged lid : this habit has been verified in respect to one of the new species described below (I. syriacus); and thus M . Guerin's concluding observation, " Elle doit etre fouisseuse comme certaines Mygales et comme les Atypes," has received a striking confirmation in fact. 1. IDIOPS FUSCUS. Idiops fuscus (Filarice mygaloides), Perty, Del. An. Art. Bras. p. 197, pl. 39. f. 5. Sphasus idiops, Walck. Ins. Apt. torn. i. p. 379. Male adult, length 4| lines. Cephalothorax suboval, but slightly convex above. Eyes eight, unequal in size; two small ones situate in front, then two of larger size, and behind these four small ones, placed in a curved line. Legs long, rather strong, attenuate towards the tarsi; relative length 1, 4, 2, 3. Palpi almost as long as the cephalothorax and abdomen, first joint forming the maxillae, last joint in the male inflated and unguiculate. Abdomen oval; sternum small, flat, subcircular. The whole spider is of a dusky black colour; the coxae of the legs testaceous ; tarsi red. At first sight similar to " Actinopus tarsalis," but in structure and position of the eyes wholly dissimilar; on the underside the colour is testaceous brown. Hab. Brazil. In the above description, M . Perty omits a strong specific character, well shown in the figure, viz. the strong and tumid radial joints of the palpi. 2. IDIOPS KOCHII, n. sp. (Plate VIII. fig. 1.) Male adult, length 7\ lines. Cephalothorax large, oval, transversely truncate before, and moderately convex above ; the lateral and posterior margins of the caput are |