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Show 1880.] OF THE GENUS ARGYRODES. 335 A single adult male of this Spider in excellent condition was contained in Mr. II. Rogers's Parana collection. This is perhaps one of the most distinct and singularly formed species, with respect to the caput, yet known. ARGYRODES SEXTUBERCULATA, sp. n. (Plate XXX. fig. 13.) Adult male, length to the apex of the abdomen rather over 2 lines. Adult female slightly larger. The cephalothorax is of a deep yellowish-brown colour; the legs and palpi reddish yellow-brown. The fore part of the caput is divided by a narrow fissure into two lobes of equal prominence, the inferior one being the strongest, rounded, consisting, in fact, of the whole of the lower part of the caput. This part bears some resemblance to the corresponding portion of A. obtusa, Cambr., but is less prominent, the upper lobe, however, being much more prominent. The eyes are in the ordinary position ; those of the hind central pair are divided by an interval but little if any thing larger than that which separates those of the fore central pair. The legs are long and slender, 1, 2, 4, 3 ; those of the third and fourth pairs are paler than the others, and marked, or somewhat irregularly annulated, with reddish brown. The palpi are short, the radial joint stronger and a little longer than the cubital; the digital joint is large but narrower, and not so large in proportion as that of A. obtusa ; while the palpal organs are, though differing a little, very similar to those of that species. The falces are long, strong, prominent near their base in front, and similar in colour to the cephalothorax. The abdomen has its hinder extremity considerably prolonged in a somewhat oblong, very slightly tapering form; on each side towards the extremity is an angular prominence, whence it tapers more rapidly, ending in a somewhat truncated form, and with four small angular tubercles or prominences in the form of a square, two above and two beneath. The colour of the abdomen is a dark yellowish brown, more or less thickly covered with pale spots, a sort of longitudinal zone along each side from the lateral prominence to the fore extremity being of a silvery hue, the hinder part of the prominence being blackish-brown. A narrow central longitudinal, tapering, obscure darkish-brown stripe runs from the anterior margin of the upperside, ending in a fine point level with the lateral prominences. The abdomen of the female is more completely covered with silvery spots than that of the male; it is shorter also, though preserving in a still more marked degree a similar form. This species is allied both to A. obtusa and A. amplifrons (postea, p. 339) ; but the greater size and different form of the caput, palpi, falces, and abdomen, will serve to distinguish it readily. Examples, in a very dilapidated state, were found among debris of web &c. in Prof. Traill's Amazons collection. PROC. ZOOL. Soc-1880, No. XXII. 22 |