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Show 1880.] OF THE GENUS ARGYRODES. 331 synonyms of the foregoing species ; but although the present Spicier resembles A. inguinalis very nearly in colours, markings, and the general character of the abdominal form, it may be easily distinguished by the more obtuse and rounded form and black colour of the apex. In A. inguinalis the apex is indeed obtuse and rounded ; but its tapering form is continued throughout, and its upper part and sides are completely silvery ; the central longitudinal band also on the fore part of the upperside is paler, and tapers without interruption to a fine point. There is considerable similarity, but still a difference, in the form of the genital process in the two species. From A. fissifrons, Camb., §, the present Spider may also be distinguished by the same characters as those which distinguish it from A. inguinalis, Thor. ARGYRODES AMBOINENSIS. (Plate XXIX. fig. 8.) Argyrodes amboinensis, Thor. Ann. Mus. Genov. xiii. p. 141 (1878). The length of the adult male isj2f lines to the spinners, and to the apex of the abdomen 3\ ; the length of the female, to the spinners rather over 3 lines, and to the extremity of the abdomen 4 lines. This fine and beautiful species has been well described by Dr. T. Thorell (I. c. supra). I have, however, thought it worth while to include here one or two figures, and also a note upon the very distinctive characters of the caput. In the absence of figures it is almost impossible to determine many of the Spiders of this group, in which the peculiar structure of the caput assumes so many forms differing from each other often in minute but important particulars. The fore part of the caput is divided into two lobes by a deep and wide cleft; the superior lobe is the smallest, and has the four central eyes on its upper side ; the inferior lobe projects considerably beyond the superior one, its extremity is subconical, and about halfway between the extremity and the base of the cleft there is, on the upperside, a strong subangular point clothed with a tuft of black hairs; three strong sinuous bristles are directed forward from the fore extremity on the upperside of the superior lobe; there are, besides these, numerous bristly hairs on and about both the lobes. As in most others of this group, the abdomen differs in form in the two sexes. That of the male is longer in proportion, and has its hinder extremity produced into a strong, somewhat cylindrical form, rounded at its "apex; it is of a yellow-brown colour, ornamented with brilliant silvery markings edged in some parts with deep blackish brown, and disposed as in fig. 8. That of the female has these silvery markings of greater extent and better defined than in the male, and with many smaller silvery spots dispersed over the sides and hinder part vide (fig. 8). The legs are exceeding long, slender, of a dull yellowish hue, coloured rather lighter than the cephalothorax, and furnished with fine hairs only. . . The palpi of the male are long, and similar to the legs in colour ; the cubital joint is longer than the radial, curved and clavate; the |