1898.] BT MR. C. S. BETTON IN BRITISH JEAST AFRICA. 515 



legs banded below almost as in 0. sexcuspidata (Pabr.), the black 

 band on the protarsus o£ 1st and 2nd not extending to apex of 

 segment as it does in mitralis, and not or hardly wider than the 

 apical white spot on the protarsus of the 4th. Abdomen coloured 

 below as in mitralis, a uniform grejdsh-brown \\itli a narrow- 

 transverse stripe behind the epigastric fold, the upperside covered 

 with a clothing of greyish-white hairs, variegated at the sides and 

 behind with brown patches and lines, sometimes with a transverse 

 mesially interrupted brown stripe behind the anterior of the 

 median sigilla, and with sometimes a median bro\^"n band extending 

 to the spinners fi'om the posterior pair of large sigilla. 



Carcqyace with its dorsal and lateral tubercles subequal in size ; 

 the length of the carapace equal to pi'otarsus and half the tarsus 

 of 1st leg, almost equal to protarsus and tarsus of 4tli ; width of 

 the head a little less than length of carapace. 



Abdomen about as broad as long ; tubei'cles very variable in size, 

 but the same in number as in 0. mitralis ; of the six forming the 

 anterior series those constituting the median pair are closer 

 together than either is to the adjacent tubercle on its outer side ; 

 the three shoulder-tubercles sometimes raised into a conspicuous 

 hump, sometimes produced into a longish pointed process, some- 

 times quite small, the median tubei'cles between them also either 

 scarcely projecting above tlie level of the integument or forming a 

 pointed conical process ; the four posterior tubercles distinct, but 

 not large. 



Vulva consisting of a black tubei'cle, the anterior half of which 

 is deeply grooved mesially ; the posterior half excavated, the 

 excavation divided by a median longitudinal ridge ; the posterior 

 rim of the excavation mesially elevated, its anterior rim formed 

 by the posterior edge of the anterior sclerite, forming two arches ; 

 the little spinuliform processes which arise from the front edge of 

 the vulva are widely separated at the base, are directed backwards 

 with a slight outward curvature, but their tips do not reach the 

 anterior arched border of the excavation. 



cj . Much smaller than 5 ; the tubercles of the carapace small, 

 especially the lateral ; legs red in colour and less distinctly banded 

 than in $ ; upperside of abdomen subcircular with truncate 

 anterior border, convex from before backwards, without tubercles, 

 with a large anterior median and three pairs of large sigilla 

 arranged in two longitudinal series, also with marginal sigilla. 



Measurements in millimetres. — 2 • Total length 22 ; length of 

 carapace 9 ; width of head 8"5 ; length of abdomen 16, width 16'5 ; 

 length of 1st leg 29, of 4th 27. 



<S . Total length 7 ; width of head 3"5 ; length of abdomen 5*5, 

 of 1st leg 13-5, of 4th 11. 



Loc. Samburu, Taru, and Marago-ya-Fundi (in the Taru desert). 



Perhaps identical with the species which Gerstacker iden- 

 tified as O. mitralis Vinson (Von der Decken's Eeisen etc. iii. 

 pt. 2, p. 491), or perhaps with that from Shoa determined as 

 G. mitralis by Pavesi (Ann. Mus. Genova, xx. p. 8) ; but certainly 



