334 REV. O. p. CAMBRIDGE ON SPIDERS [Apr. 20, 



Argyrodes bicornis, sp. n. (Plate XXIX. fig. 12.) 



Adult male, length to the spinuers 1 Hue, to the apex of abdomen 

 rather more than 1 1" line. 



It is perhaps questionable whether this Spider should not be 

 included in the genus Ariamnes (Thor.) rather than in Argyrodes, 

 the two genera being very closely united ; believing it, however, to 

 have more in common with the latter than with the former genus, 

 I have, for the present at least, placed it in Argyrodes. 



The form of the caput is very striking, and distinguishes it at a 

 glance from all the Spiders of this singular group yet known to me. 

 The posterior lobe (comprising the ocular area) has its centre pro- 

 duced into a strong, horn-like, slightly curved, tapering, obtusely- 

 pointed eminence, directed forward, surmounted with a tuft of long, 

 strong, bristly hairs also directed forwards ; immediately below the 

 fore central pair of eyes, at the upper part of the clypeus (which 

 slopesconsiderably forwards), is another horn-like prominence directed 

 forwards in a parallel direction with the other, and of about equal 

 length but not nearly so strong, straight, and slightly enlarged at 

 its extremity, which is also furnished with some long bristly hairs 

 directed rather backwards, so as to meet those directed forwards 

 from the extremity of the posterior horn. 



The colour of the cephalothorax is pale yellow, with a suffusion 

 of reddish brown on the margins, mostly on that of the thorax. 



The legs are long and slender, especially those of the first pair ; 

 their relative length is 1, 2, 4, 3; and they are similar in colour 

 to the cephalothorax ; the tibiae, tarsi, and metatarsi of those of the 

 first and second pairs reddish yellow-brown. They are furnished 

 pretty thickly with fine hairs, many of those on the tibise being 

 erect. 



The palpi are similar to the legs in colour, moderately long, the 

 radial and cubital joints short and of equal length ; the digital 

 joint is rather small, oval, and yellow-brown, with a small notch or 

 cleft at the extremity ; the palpal organs are compact, and neither 

 very prominent nor complex. 



The eyes of the fore central pair form a line at least as long 

 as the hind centrals, if not rather longer, and each is very near to, 

 but not contiguous with, the fore lateral eye on its side. The four 

 centrals thus form, as nearly as possible, a square. ^ 



Tiie /a^ce*- project considerably forwards, and, with the maxillae, 

 labium, and sternum, are similar in colour to the cephalothorax. 



The abdomen has its upperside prolonged into a long tapering 

 eminence directed a little backwards in a sloping form, the apex 

 being bifid in a somewhat fish-tail form. It is of a dull whitish 

 yellow-brown colour, indistinctly marked on each side at its anterior 

 extremity with a rusty- red-brown hue, and with a suffusion of the 

 same colour on the upperside towards and round the apex ; some 

 traces of a similar hue are also visible on the hinder part ; and there 

 is a central longitudinal line of the sam.e on the underside. 



It is very possible that a series of examples would show some 

 variations in the colour and pattern of the abdomen. 



