620 The Systematic Position of the Genus Hadrotarsus. 



ventral sclerites. The ventral sclerites are two in number 

 and subcqual in length ; they are separated from each other 

 by a transverse band of thick membrane. The anterior 

 sclerite extends forwards to the pedicle. In front of its 

 posterior border in the middle line is the very distinct 

 epigyne ; the lung-sacs lie at its sides, their spiracles being 

 upon its postero-iateral angles. The tracheal spiracles are 

 situated in the middle of the membranous band; they appear 

 as a pair of contiguous round dark spots, surrounded by a 

 circular rim. The posterior plate is narrowed behind and 

 extends back to the spinners. The four visible spinners 

 form with the anal tubercle a compact cluster at the extreme 

 posterior end of the abdomen. 



Simon placed the Hadrotarsidje provisionally between the 

 Oonopidie and Dysderidas, but the well-developed epigyne 

 serves to separate them entirely from the neighbourhood of 

 these families and to place them amongst the ecribellate 

 entelegynous forms. Simon also points out that they have 

 '' des rapports ti^s serieux " with certain Theridiidas, notably 

 with Fholcomma, but more especially with Paculla and Tttra- 

 hlemmo. Hadrutarsus has the high clypeus, the conical 

 cluster of spinners, &c. of the Theridiidw, the broad sternum, 

 triangular labium, obliquely inclined maxilla?, strong attenuate 

 mandibles with long slender arclied fangs, and the long tarsi 

 described by Simon as typical of the Paculle£e {loc. cit. p. 570). 

 Moreover, the irregular shape and general appearance of the 

 posterior median eyes in Hadrotarsus suggest that these 

 organs are in process of atrophy. Were the obliteration to 

 be completed, the remaining six eyes would not differ greatly 

 from the six eyes of Paculla. As for the abdomen, in the 

 presence of the large dorsal scute, of the lateral and posterior 

 integumental folds, and of the ventral scutes it is almost iden- 

 tical with that described and figured by Simon as seen in 

 Tetrahlemma [he. cit. p. 3, fig. b, and p. 571, fig. 584), 

 except that the integumental folds are not strengthened with 

 chitinous bands (erroneously compared by Simon -with the 

 tergal plates of Lipkistius), and the posterior ventral plate is 

 relatively larger and undivided. Simon was not able to deter- 

 mine with certainty the position of the spiracles in Tetrahlemma 

 and Paculla, but supposed them to open upon the posterior 

 border of the anterior ventral scute, where they are placed, in 

 fact, in Hadrotarsus. Cambridge, however, described the 

 spiracles in Tetrahlemma as situated close together towards 

 the middle of the ventral surface behind the anterior scute 

 (P. Z. S. 1873, pi. xii. fig. 1 c, p. 115). However that may 



