1 898.] BT MB. C. S. BETTOX IN" BRITISH EAST AFBIOA. 521 



Hist. (6) XX. p. 260, fig. 4), that no detailed description is 

 necessary ; the principal difference lying in its much smaller size, 

 the adult male measuring with the mandible only 18 mm., whereas 

 S. sericea is as much as 30. Moreover, although the tergal plates 

 of the abdomen in zehrina are narrowly margined with black with 

 a broad black median doi-sal band, there is on each side of the 

 latter a conspicuous broad yellow stripe, each being almost halt' 

 the width of the median black stripe. In *S^. sericea the corre- 

 sponding yellow stripe is very narrow in comparison. 



Measurements in millimetres. — S • Total length of trunk 15, with 

 mandibles 18; width of head 3; length of palp 17, of 1st leg 16, 

 2nd leg 13, 3rd leg 17"5, 4th leg 29 ; tibia, protarsus, and tarsus of 

 palp 5-5 ; tibia of 4th leg 5, protarsus 5*5. 



Loc. Maziwa ya Tagari, in the Tarn desert. 



Two male examples. 



Genus Zebiassa Pocock. 

 Zeriassa, Pocock, Ann. Mag. Nat. Hist. (6) xx. p. 255 (1897). 



Zebiassa sbinitlosa, sp. n. (Plate XLII. fig. 15.) 



Colour. Upperside of mandible, head, thorax, and abdomen a 

 uniform reddish or earthy brown ; two indistinct darker stripes on 

 the mandible ; ocular tubercle black, only the tips of the fangs 

 reddish brown ; palp with tibia, protarsus, and distal third of the 

 femur black; tarsus and basal two-thirds of the femur clear 

 yellow ; the joints between the femur, tibia, and protarsus slightly 

 paler ; 1st and 2nd legs yellow, with the exception of the fuscous 

 distal end of the femur ; 3rd and 4th legs also with the tibia 

 distally black and the femur lightly infuscate, the rest of these 

 limbs pale ; lower surface of thorax and abdomen pale. 



Head-plate equalling in width about two-thirds the length of 

 the tibia of the palp and five-sixths the length of the protarsus of 

 the 4th leg, as long as the tibia and one-third of the protarsus of 

 the 3rd leg ; studded with spinules ; ocular tubercle prominent, 

 high and wide. 



Mandibles inflated, abruptly narrowed at the base of the fang, 

 armed with longish spines above, the upper fang projecting far 

 beyond the base of the flagellum, armed with a series of seven 

 triangular but not long teeth, the first very small, placed a long 

 distance behind the tip of the fang and close to the second, which 

 is large and just below the base of the recurved portion of the 

 flagellum ; third tooth small, nearer to the fourth, which is also 

 large, than to the second, the remaining three small and equally 

 spaced ; one small tooth on the inner side nearly on a level with 

 the seventh tooth of the outer series ; lower fang armed with 

 three distinct teeth, the first and third subequal, the second 

 smaller and nearer the second. 



Flagellum with high, convexly rounded membranous portion: 

 the recurved terminal portion short, scarcely surpassing the 

 membranous portion ; on the inner side of the upper fang are a 

 couple of stout spines lying below the flagellum. 



