THE AFGHAN DELIMITATION COMMISSION. 119 



Measurements (in millimetres) of largest specimen. — Total length 62 ; length of head- 

 plate 5, width 10 ; length of chelicera 12, width 1J ; length of tarso-metatarsus of maxil- 

 lary palp 7, of tibia 6, of femur 7-|. 



Two gravid females between Hari-rud valley and Meshed. 



One of the specimens is slightly smaller than the other, with the head-plate ochraceous 

 and not fuscous. Moreover, it presents another feature by which it may be recognized, 

 not only from the specimen with which it was captured, but, to the best of my belief, 

 from all specimens of Rhax hitherto examined. This peculiarity, the importance of 

 which, owing to lack of material, it is impossible to estimate, is the presence of a third 

 and median seta occupying a position on the ocular tubercle midway between the two 

 setae which have been considered so important a characteristic of this genus and others. 

 All the specimens of Rhax that have been described have possessed two and only two 

 ocular sette ; yet inasmuch as these two Afghan individuals are so like each other in all 

 those features which have been found to be of value for the determination of the species 

 of this genus, I am unwilling to consider the smaller as specifically distinct from the 

 larger on the strength of the existence of this median hair. Therefore, until the con- 

 stancy of the occurrence of this seta can be tested by the examination of a number of 

 individuals, it can only be looked upon as an abnormal development. 



The species of Rhax are mostly rendered conspicuous by their colours ; and this species 

 may be at once recognized from others by its entirely white abdomen. 



ACARIDEA. 



10. Hyalomha gkossum (C. Koch). 



Hyalomma grossum, C. Koch, Arch. f. Naturg. s. i. p. 220; id. Uebersicht des Arachnidensystems, 

 iv. pi. ii. fig. 8. 



Two specimens ( ? ) taken from a camel, between Hari-rud valley and Meshed. 



CHILOPODA. 



11. SCOLOPEXDRA TRUXCATICEPS, sp. n. (Plate XIII. fig. 7.) 



Ochraceous or testaceous, the dorsal plates of the anterior and central portions of the 

 body slightly olivaceous. 



Antennae composed of 19 segments, of which the four distal are bare, the rest very 

 faintly pubescent. 



Head-plate pentagonal, with straight posterior margin, meeting but not covering the 

 anterior portion of the first dorsal plate; marked in its posterior half by two very faint 

 anteriorly diverging sulci, not punctured. Width equal to width of last dorsal plates. 



Prosternal plates of the maxillary sternum almost in contact ; each plate furnished 

 with four teeth, of which the three internal exhibit various grades of concrescence. 

 Basal tooth simple or very slightly denticulated. 



Dorsal plates, except the first and last, bisulcatc ; the last seven or eight with raised 



