Stridulating-organ in Scorpions. 61 



difference between the two species. The pectines in R.junceus 

 are expanded exactly as in R. BoreUii, and the distal edges 

 of the teeth bulge in almost precisely the same way, but the 

 differentiation of the striee is carried to a greater extreme. 

 Along the edge of each tooth there is a distinct series of small 

 tubercular elevations, which are largest where they cross the 

 thickened bulging area, becoming smaller both above and 

 below it. These elevations are very distinctly striated, and 

 the striae appear to be practically restricted to them (PI. IV. 



fig- 4). 



In R. laticauda, Thor., the granules on the sternite are 

 relatively as coarse as in R. Borellii) but the area is less 

 depressed and less sharply differentiated both in front and 

 towards the middle line than in that species. Also the poste- 

 rior surfaces of the pectinal teeth are less visibly striated and 

 the distal edges of those opposable to the granular area are 

 straight and without the characteristic bulge so noticeable in 

 R. Borellii and R. junceus. In all these features the organ 

 in R. laticauda is less specialized than in the two species just 

 mentioned. 



The remaining species of Rhopalurus are unknown to me. 

 Those who have had the opportunity of seeing and describing 

 R. princeps have made no mention of any structural peculi- 

 arities in the pectines or in the first abdominal sternum. 

 According to Kraepelin, who has seen the typical examples, 

 however, this species is nearly related to R. laticauda. 

 Hence it is permissible to suppose that it also possesses a 

 stridulating-organ similar in its general features to the stiidu- 

 lator of that species. In the case of R. agamemnon the last- 

 mentioned author states that the pectines are expanded and 

 the sternum grooved and depressed as in R. junceus, but that 

 the sternum differs from that of R.junceus in being distinctly 

 granular on the median triangular area. This peculiarity, in 

 which R. agamemnon holds a unique position in the genus, 

 suggests that the median area in question constitutes an 

 integral part of the stridulating-organ. Whether the de- 

 pressed areas are granular or shagreened, or neither, is at 

 present unknown. 



Two other important facts connected with Burchell's 

 observation remain to be mentioned. The first is the discovery 

 of stridulating-scorpions in America : those in which soundino-- 

 organs are known or supposed to exist have hitherto been 

 recorded from the Mediterranean, Oriental, and Ethiopian 

 regions. The second is the announcement of the exact 

 locality of R. Borellii. R. princeps occurs in Hayti, R.junceus 



