766 KEV. O. p. CAMBRIDGE ON NEW ARANEIDEA. [JlUie21, 



Aphantochilus, Cambr. (P. Z. S. 18/0, p. 744). This latter genus 

 was conjectured to belong to the Mjrmecidse; but I have now no hesi- 

 tation in forming for it and the genus Bucranium a separate family 

 (Aphantochilidse), near to the Thomisidse. More extended remarks 

 on all these points will be found in the subjoined descriptions. 



Order ARANEIDEA, 



Fam. TheridiidjE. 



Gen. nov. Thwaitesia. 



This genus is nearly allied to Theridion, but may be easily distin- 

 guished by the conically elevated abdomen, the shorter, stronger 

 maxillse, the more prominent ocular area, the larger eyes, which, 

 although preserving a similar general arrangement, are divided into 

 two well separated groups of four each, each group formed by one 

 of the lateral pairs and the hind and fore lateral eye next to it, 

 all four being almost, or quite contiguous to each other ; the fore 

 central pair are smallest, and form a shorter line than the hind cen- 

 trals. The legs also are armed with distinct spines on the genual 

 and tibial joints of all four pairs ; while the metatarsi and tarsi of the 

 fourth pair are armed with numerous spine-like bristles, a row near 

 the inner side of the tarsi being curved and serrated. This latter 

 armature, however, is much less strong in the male than in the 

 female ; indeed in the male I could not distinguish any serrations. 

 The relative length of the legs, which are rather long and slender, is, 

 as far as I could judge from the damaged condition of some portions, 

 4, 1, 2, 3, the difference between those of the first and fourth pairs 

 being but slight. The falces are weak, straight, and subconical, 

 and the fang likewise small and weak. The sternum is heart- 

 shaped. 



Thwaitesia margaritifera, sp. n. (Plate LXVI. fig. 1.) 



Length of the adult male Ig line, that of the female being rather 

 more than 2 lines. 



The cephalothorax is pale yellow, some examples having an indis- 

 tinct reddish-brown central line from the occiput backwards ; and 

 two (females) had a broad brown central band from and including 

 the eyes to the hinder extremity of the thorax. The thorax is 

 gibbous above, with the thoracic indentation strong ; the ocular area 

 of the caput projects forwards, the eyes (disposed as above men- 

 tioned) occupying the whole of the upper extremity of the caput ; 

 the height of the clypeus considerably exceeds half that of the facial 

 space, and projects well forwards. 



The legs are similar in colour to the cephalothorax, the articula- 

 tion of the tibiae and metatarsi of the first and fourth pairs having a 

 tinge of reddish brown, and a portion at the extremities of the meta- 

 tarsi of these pairs being also dark reddish brown. On the upper 

 side of each of the genual joints is a distinct black spine ; and on each 

 of the tibise are two others, one near the middle and one near the 

 anterior extremity. 



