144 
Transactions of the Royal Society of South Africa. 
Key to the South African Species of the Genus Opisthophthalmus. 
(1) Median groove of carapace with a well-developed Y-shaped fork in 
front: eye tubercle situated far behind the middle of tke carapaces 
a. Under side of first four caudal segments convex, not grooved longi- 
tudinallij, the median crests quite obsolete, represented at most hy 
Mack lines. Superior process of tarsi much shorter than the lateral 
lobes. (a^-V.) 
a^ External lobe of tarsus IV with 3 spines ; male with all the 
sternites and lower surfaces of caudal segments I-IV smooth 
and polished ; carapace more finely granulated than in ater 
0. schlechteri Pure. 
External lobe of tarsus IV toith 4 spines. 
d?. Abdominal sternites and first 3 caudal segments in- 
feriorly smooth and polished, caudal segment lY some- 
what roughened below ; tarsus IV with 1 external 
spine inferiorly. Entirely black . . . Male of O. ater Pure. 
b". Last sternite, and first 4 caudal segments inferiorly, 
densely and finely granular in the male, smooth in the 
female except on caudal segments III and IV, which are 
thickly granulated ; tarsus IV without an external spine 
inferiorly. Ochraceous to brown . . . . O. granicaud a Vuvc. 
b. Under side of caudal segment IV toith median and lateral keels, the 
surface distinctly grooved beitoeen the keels, (a-'-b'.) 
a'^. Last sternite always coarsely, though often someivhat tveakly 
granular, at least, in the middle : tarsus IV ivith a single 
internal roio of spines below (in capensis occasionally with a. 
minute extsmal spine also) and with 3-4 spines on the extertial 
terminal lobe. (a''-b''.) 
a''. Interocular area smooth or weakly granular, not bordered on 
each side by a strip of coarse granules ; all the sternites 
coarsely granular, excepting sometimes the first sternite of 
the female; tarsus IV with 3-4 spines on the external lobe, 
the superior process shorter than the lobes . . . O. pictus Kraep. 
b^. Interocular area granular or rugoso-granular in the anterior 
half; sides of carapace coarsely granular, especially along the 
borders of the interocular area ; sternites II-V in the male, 
and V with the hinder portion of IV in the female, granu- 
lated, (a^ and b\) 
a^. Finger keel and upper crest of brachium composed of a 
row of coarse granules ; outer part of upper surface 
of hand coarsely granular ; superior process of tarsi 
shorter than the lateral lobes ; external lobe of tarsus 
' IV with 3 spines' ....... O. granifrons Voa. 
* O intermedins and O.fossor, having occasionally a partially developed fork, may 
sometimes fall in this section: see sec. 3. It should be understood that the several 
main sections here distinguished are not sharply defined natural groups, although as 
far as possible each species is arranged alongside its nearest allies in this key. 
