XII CLASSIFICATION 307 
The DIPLOCENTRINAE have a spur under the aculeus. They 
form a small group of only eight species. The principal genus, 
Diplocentrus, is entirely Neotropical, but Nebo has a single Old 
World representative in Syria. 
The URODACINAE, with the single genus Uvodacus, are 
Australian scorpions. As in the next sub-family, there are 
rounded lobes on the tarsi, but there is only a single keel on the 
“tail,” and the lateral eyes are two in number. Six good and 
three doubtful species are recognised. 
The SCORPIONINAE are Asiatic and African forms, and are 
recognised by the tarsi having a large lobe on each side, by the 
convex upper surface of the “hand,” by the presence of two 
median keels on the “tail,” and by the possession of three lateral 
eyes.  Palamnaeus (Heterometrus) has sixteen species in the 
Indian region. There are about thirty species of Opisthoph- 
thalmus, all natives of South Africa. Pandinus includes about ten 
species, but there are only two species of the type genus Scorpio, 
S. maurus and S. boehmer. 
The sub-family HEMISCORPIONINAE was formed for the 
reception of the single Arabian species Hemiscorpion lepturus. 
Its most striking characteristic is the cylindrical vesicle of the 
tail in the male. 
The IscHNuRINAE differ from the Scorpioninae chiefly in the 
absence of the tarsal lobes, the presence of a well-marked finger- 
keel, and the generally more depressed form of the body and 
hand. In the opinion of some authors they should be separated 
from the Scorpionidae as a distinct family, the Ischnuridae. 
There are more than twenty species, divided among six genera. 
The type genus Jschnurus has only the single species /. ochropus. 
There are eight species of Opisthacanthus, which has representa- 
tives in Africa and America. 
Fam. 3. Chaerilidae.— Sternum pentagonal with median 
depression or “sulcus” rounded posteriorly. Two pedal spurs. 
Stigmata circular. Two lateral eyes with a yellow spot behind 
the second. Pectines very short. 
This small family has the single genus Chaerilus with but 
seven species, natives of the Oriental region. 
Fam. 4. Chactidae.—Zwo pedal spurs. Two lateral eyes 
(or, rarely, no eyes) but without yellow spot. Characteristic 
dentition on movable finger of “ hand.” 
