316 Mr. R. I. Pocock on new Genera 
Family Scorpionide. 
Subfamily [scuwverryr. 
OPISTHOCENTRUS, gen. nov. 
(Pl. XIV. figs. 2 and 3.) 
Differs from Opisthacanthus, Peters, of which elatus, Ger- 
vais, is the type, in that the anterior border of the carapace is 
less deeply excised, the lateral eyes less prominent and either 
subequally spaced or with the distance between the posterior 
and median greater than that between the median and anterior, 
in having only a small projection on the anterior aspect of the 
brachium, in having the genital operculum very much smaller, 
being shorter, in fact, than the side of the sternum, and much 
wider than long, in having the pectines narrower at the base, 
and the tactile area of the teeth limited to the posterior distal 
extremities of these organs. 
Type, O. africanus (Simon). 
I establish this genus for those species of Opisthacanthus 
that have been described from Africa. So far as my exami- 
nation extends these African species differ in a number of 
characters from the South American form Opisthacanthus 
elatus. It may be that these characters are of small value in 
themselves, and it would be bold to assert that every one of 
them is of itself of generic importance. But the aggregate 
value of them all, coupled with the wide difference in the 
geographical distribution of the two types, is sufficient, I 
think, to justify the adoption of the view of their importance 
that is here put forward. 
In Opisthacanthus elatus the carapace is deeply excised in 
the middle line, the lateral eyes are prominent, the space be- 
tween the anterior and median being greater than that be- 
tween the median and posterior; there is a large dentiform 
prominence upon the brachium as in Lschnurus and Hormurus ; 
the genital operculum is large, being nearly as long as wide, 
and longer than the side of the sternum, in the female it is 
heart-shaped, being noticeably produced posteriorly ; the 
pectines are generally very wide at the base, owing to the 
size of the basal intermediate lamella, and the teeth appear 
to have been rotated so that the tactile areas which generally 
look distally and externally are entirely external and extend 
over nearly the whole of the exposed surface of the organ (at 
least in the male). 
