122 MR. R. I. pocoCK ON THE SCORPIONS [Mar. 18, 



denticles are arranged in a long simple longitudinal series, which only 

 in the distal half divides into a number ofobhque short rows; the 

 internal series consists of enlarged teeth set singly and at a distance 

 from the series from which they arose : the external teeth of the 

 external series are also arranged in a single row, the individual teeth 

 being close to the median series and alternating with, but not forming 

 a transverse line with, those of the internal series. 



The genus is further remarkable for the great size of the tail. 



Genus Buthus, Leach. 



Buthus (Leach), Thorell, Etudes Scorpiol. p. 8 — type europceus 

 (Linn.). 



This genus is unknown in America and Australia, but, including 

 all the subgenera here admitted, is widely distributed elsewhere, 

 being especially abundant in Africa and the ^lediterranean district. 



Subgenus Rhoptrurus, Karscb. 

 (Plate XIH. figs. 1, 2, and Plate XIV. fig. 1.) 



Odonturus, Karsch, Sitz. Ges. nat. Fr. 187!', p. 1 19 (noni. prseocc). 



Rhoptrurus, id., Berl. ent. Zeits. xxx. p. 77 (188<)). 



Babijcurus, id. ibid. 



Ilab. S. Africa, Madagascar. 



^lovable digit of chelicerae with two teeth on the inferior border. 



In the digits of the chela; the posterior ends of the median rows of 

 denticles are not enlarged, but are bent outwards, thus coustitviting 

 the external series ; the internal series is formed by the enlarged 

 and slightly separated anterior tooth of each median row. The 

 cephalothorax is not keeled ; the tergites have one median keel. 



The tail is powerful or moderate, strongly keeled or almost without 

 keels : there is a spine beneath the aculeus. 



The pectinal teeth are all alike. 



The sexes may differ in many ways, as in Isomef.rits ; thus the S 

 of R. kirJiii has a widened tail, a widened hand, and a space between 

 the base of the digits ; in R. baronii the pectines of the cJ are much 

 larger than in the $ . 



Of all the subgenera o^ Buthus this one comes nearest to Isometrus, 

 uniting Isovietrus with I'arabuthus. Fiom Isometrus it may be 

 distinguished by tiie dentition of the chelicerae, and from Farabuthus 

 by the spine beneath the sting, the much less strongly dentate or 

 granular tail, and by the arrangement of the denticles on the digits 

 of the chelse. The gQWXXi Babycurus vislS, separated from Rhoptrurus 

 on the strength of the greater slenderness of the tail ; but since 

 this is merely a sexual character belonging to the female, the genus 

 caimot well be retained. 



This genus contains the following species : — 



R. dentatus, Karsch (under Odonturus), Sitz. Ges. nat. Fr. 

 Berlin, 1879, p. 119 ; Mombas. 



R. biittneri, id. (under Babycurus), Berl. eut. Zeits. xxx. p. 7S, 

 pi. iii. fig. 1 (1886) ; Gaboon. 



R. centrurimorphus, id. ibid. fig. 2 ; Madagascar ; and the three 

 species described below (pp. 137-141). 



& 



