Stridulating-organ in Scorjnons. 59 



purpose therefore was carried out upon the three spirit- 

 preserved examples the Museum possesses, namely, the type, 

 an adult female, an immature specimen of the same sex, and 

 an adult but badly preserved male. 



Although only described seven months ago, this species 

 has been known to me for ten years. Briefly told, its history 

 and that of its allies is as follows : — In 1893 * I pointed out 

 that two American species of Buthidas identified with the 

 Scorpio junceus of Herbst and Tityus agamemnon of C. Koch 

 differ from their allies in the structure of the pectines and of 

 the first sternal plate of the abdomen. The pectines are 

 unusually broad in their proximal half, and the overlying 

 area of the sternal plate is depressed, the grooves which 

 ordinarily pass forwards and inwards from the inner extre- 

 mity of the stigma being exceptionally deep and lying nearer 

 to the middle line, so that they define a narrow, smooth, tri- 

 angular area, standing at a higher level than the depressed 

 lateral portion already mentioned. On the strength of these 

 structural features the genus Heteroctenus was established for 

 these two species. It was also stated that Heteroctenus 

 junceus differs from the form then referred to H. agamemnon 

 in having the depressed area smooth instead of closely and 

 finely but distinctly granular. Subsequently, as a result of 

 the publication of Dr. Kraepelin's monograph -j- on the scor- 

 pions, it was found that these two species can scarcely be 

 separated generically from the species described as Rhopalurus 

 laticauda by Thorell and R. princeps by Karsch. Further- 

 more, the description given by Kraepefin, presumably from 

 an examination of the type of Tityus agamemnon, proved my 

 previous determination of agamemnon to be erroneous. I 

 therefore redescribed the species so determined under the new 

 name Borellii \, and at the same time attempted to show 

 that the five species under discussion — namely, junceus, lati- 

 cauda, princeps, agamemnon, and Borellii — possess certain 

 characters in common of sufficient systematic value to justify 

 their separation from the series forming the genus Gentru- 

 roides, with which Kraepelin associated them, and to demand 

 their recognition as a distinct genus for which the name 

 Rhopalurus is available §. 



The significance of the depressed sternal areas and of the 

 expanded pectines in R. Borellii and R. junceus was always 



* Journ. Linn. Soc, Zool. xxiv. p. 393. 



t Das Tierr., Scorpiones et Pedipalpi, pp. 94-95 (1S99) 



X Ann. & Mag. Xat. Hist. (7) x. p. 375 (1902). 



§ Biol. Centr.-Amer., Arachn. Scorp. p. 37 (1902). 



