Ethiopian Species o/'Ischnuringe. 313 



a 1 . Feet furnished below with paired bristles 

 and along the middle line with a series of 



delicate spinules Iomachus, Poc. 



b l . Feet furnished below with paired spines; 



without a distinct median row of spinules 



(at least in the South -African species). 



« 2 . Tail very strongly compressed ; body and 



claws flatter ; many pores on the outer 



border of the lower surface of the hand 



and forearm Hadogenes, Kraep. 



¥. Tail stouter ; body less flat ; only a few 

 pores on the outer border of lower side 

 of the hand and forearm Opisthacanthus, Pet. 



Genus Opisthacanthus, Peters. 

 Opisthacanthus crassimanus, sp. n. 



Closely allied to 0. Jonesii (Poc.), from Murchison Range, 

 Transvaal, but very much smaller (cf. measurements) and 

 possessing a distinct ridge of granules on the humerus, sepa- 

 rating its anterior from its upper surface, and also in having 

 the crests upon the last abdominal sternite and on the lower 

 surface of the first caudal segment smooth instead of granular. 



Measurements in millimetres. — Total length 48 ; length of 

 carapace 6'5, of tail 225, of hand-back 4*8, of movable digit 6 ; 

 width of hand 6'5. 



hoc. East London [H. A. Spencer). A single male ex- 

 ample. 



This example has been selected as the type ; but the 

 Museum has two others of apparently the same species, one 

 from Caffraria and the other from Natal, from the collection of 

 the late F. P. Pascoe ; also three young examples from 

 Basutoland (R. G. Wroughton), which are provisionally 

 referred to this species. 



It is possible that these examples will prove to be the 

 young of C. Jonesii, but the only sign of immaturity shown 

 by the type is the absence of lobes on the digits. More- 

 over, analogy lends no support to the view that the distinctive 

 features of this form are due to immaturity. The interest 

 attaching to the species lies in the fact that the presence of 

 the anterior crest on the humerus bridges over one of the 

 distinctions between the genus Cheloctonus and Opisthocentrus. 



It may be added that the spine-armature of the tarsi in 

 these two species resembles that of the West-African species 

 0. africanus, Sim., there being three posterior and two ante- 

 rior spines, with the distal inferior angle of the tarsus tipped 

 with a bristle, and not with a spine as in 0. validus, Thor., 

 and 0. asper (Pet.). 



