Mr. J. Blackwall on new Species of Sjnders. 211 



Apt. torn. ii. p. 291) is a mucli larger spider than the T. triste 

 of Hahn and Koch, and is probably specifically identical with 

 the Phrurolithus hmatus of the latter author (Die Arachn. 

 Band vi. p. 107, tab. 206. fig. 509). 



Theridion grossum. 



Theridion grossum, Walck., Hist. Nat. des Insect. Apt. torn. ii. p. 328. 

 Tkeridium grossum, Koch, Die Arachn. Band. iv. p. 112, tab. 140. fig. 321. 



Length of the female | of an inch ; length of the cephalo- 

 thoi'ax ^, breadth f ; breadth of the abdomen j^^ ; length of an 

 anterior leg | ; length of a leg of the third pair y^^ . 



As the adult female of Theridion grossum, which, like certain 

 species of the genus Latrodectus, does not acquire its sombre 

 hue till it arrives at maturity, has been well described by Koch, 

 I shall merely supply, in addition to the measurement given 

 above, a few particulars that have been omitted. 



The eyes are disposed on the anterior part of the cephalo- 

 thorax in two transverse rows ; the four intermediate ones de- 

 scribe a trapezoid, the two anterior ones, which form its shortest 

 side, and are seated on a protuberance, being the smallest and 

 darkest- coloured of the eight; the eyes of each lateral pair are 

 placed obliquely on a tubercle and are contiguous. The maxillae 

 ai'e obliquely truncated at the extremity, on the outer side, and 

 inclined towards the lip, which is somewhat quadrate, being 

 broader at the base than at the apex. These parts have a red- 

 dish-brown hue, that of their extremities being yellowish-white. 

 The sexual organs, which are well-developed and semicircular, 

 have their posterior margin curved and prominent, and are of a 

 red-brown colour, that of the branchial opercula being dull 

 yellow. 



The immature female and adult male of this species do not 

 appear to be known to arachnologists. They differ remarkably 

 from the adult female, the upper part of the abdomen being of 

 a dull yellowish-white hue, densely freckled with minute white 

 spots, and having a scries of broad, curved, transverse, soot- 

 coloured bands in the middle, whose extremities extend to the 

 sides. The legs have a brownish-yellow hue. 



The male is much smaller than the adult female, and its 

 slender legs are much lighter-coloured. Its palpi are short, and 

 the radial, which is larger than the cubital joint, is produced at 

 its extremity, on the outer side ; the digital joint is of an elon- 

 gated oval form and of a reddish-brown colour ; it is pointed at 

 the extremity, convex and hairy externally, concave within, 

 comprising the palpal organs, which are well developed and are 

 terminated by a large curved spine, whose extremity is in con- 



