76 Mr. K,. I. Pocock on a new Generic Distinction 



great value ; and since Prof. Kraepelin has recently shown 

 that the species referred to PalamncBUS are in reality more 

 nearly allied to the Indian species of Scorpio than the latter 

 are to the African species of this genus, it is probable that 

 all arachnologists will be content to abide by his decision 

 that the thickness of the inner edge of the hand in longimanus 

 and its allies is not of sufficient value to be accorded generic 

 rank. Prof. Kraepelin, in fact, regards all the species re- 

 ferred by Thorell and others to Scorpio or Pandinus and 

 PaJamnceus to the genus Scorpio, which therefore extends 

 over tropical Africa, India, Ceylon, Burma, Siam, Sumatra, 

 Java, and Borneo ; but at the same time he points out that 

 the species involved fall into two divisions, based upon a 

 structural feature which, as is so often the case, coincides 

 with the division that would be drawn upon geographical 

 grounds. The African forms, for example, are recognizable 

 from the Asiatic * by the presence on the posterior side of the 

 lower surface of the brachium of the chela of a ridge, in front 

 of which run two or more rows of piliferous pores, this ridge 

 and the definite rows of pores being hardly perceptible in the 

 Asiatic species. This character Prof. Kraepelin does not 

 look upon as of generic importance. 



Whilst engaged, however, in investigating the remarkable 

 stridulating-organs presented by the scorpions of this section f, 

 I discovered that these organs furnish a valuable additional 

 distinctive character between the- Ethiopian and Oriental 

 species. In each case the instrument consists of a cluster of 

 spiniform notes and of an adjacent area of granules, which, 

 by being rubbed against the tips of the notes, throw them into 

 a state of vibration ; and in botli cases the organ is situated 

 between the basal segment of the chela and the corresponding 

 segment of the first walking-leg. But, as the late Prof. Wood- 

 Mason pointed out J, the cluster of notes in the Indian 

 species is situated on the coxa of the chela and the granular 

 area on the coxa of the first leg. I find in the African 

 species, on the contrary, that the notes are placed upon the 

 maxillary process of the first leg and the cluster of granules 

 upon the coxa of the pincer. These organs, it seems, may 

 well be regarded as of generic importance ; and in this case 

 the term Scorpio must, of course, be retained for the African 



* With the exception of the so-called Sumatran s^Qcies, pallidus, which 

 has the characters of the African forms. But if my suggestion respecting 

 the locality of this species prove correct, this apparent exception will 

 fall to the ground {vide Ann. & Mag. Nat. Hist. (6) xvii. p. 435, in note). 



t For descriptions and figures of these organs see * Natural Science,' 

 July 1896. 



\ Proc. Ent. Soc. Lend. 1877, pp. xviii, xix. 



