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 

 fourtli pairs are paler than the others, and marked, or somewhat 

 irregularly anuulated, with reddish brown. 



The jialpi 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. 



'Yhe fakes 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 



