1 66 ON NEW AND RARE BRITISH SPIDERS. 



longer though of nearly about the same thickness, with its upper 

 end blunt-pointed, and bending over just into contact with 

 the extremity of the anterior lobe ; between the lobes is an oval 

 or slightly semi-circular gap. The general characters of all the 

 species of this group are very much alike, as also is the structure 

 of the palpi and palpal organs, though differences in these are 

 apparent. The species with which the present seems to be most 

 closely allied is D. fProsoponcusJ crassiloha Sim. It should be 

 noted that in the present species the hind-central pair of eyes 

 are placed further back from the fore -extremity of the posterior 

 lobe than in some of the other species of the group. It is very 

 possible (M. Simon says — Arachn. de France, V. p. 576 — "it is 

 not impossible ") that all these species are only local forms of 

 one of them, i.e., the one first described, Diplocephalus {Pfoso- 

 poncus) forainiiiifcr, Cambr."^' The female of the spider now 

 recorded is the first of this sex hitherto known in this special 

 group, and the genital aperture, though bearing some resem- 

 blance in its form to that of D. cristatus, may yet be distinguished 

 with certainty. (See fig. 8a.) The discovery of the females of 

 others will help to decide the question of their specific identity 

 or distinction. 



Adults of both sexes were sent to me in 1902 and 1903 from 

 Hexham by Dr. A. R. Jackson, by whom they were found among 

 debris on the banks of the river Tync. 



Diploeephalus Jacksonii, sp. n. Fig. g. 



In size, colours,' and general appearance this spider is much 

 like the foregoing, D. adjacens, but the male may be distinguished 

 from it at a glance (as well as from all others of the group yet 

 known to me) by the large comparative size and bluff form of 

 the anterior lobe of the caput, as well by the less height and 

 different form of the posterior lobe. The small interval between 

 the two lobes is almost hidden by short stiff hairs, which meet 



* Pioc. Zool. Soc, Lon., 1875, p. 207. pi. xxviii., fig. 15. 



