hetween Scorpio and Palamnasus. 77 



species, while to all the Asiatic forms tliat present the instru- 

 ment discovered by Wood-Mason, Thorell's name Palamnceus 

 may be applied, though the definition of the genus will have 

 to be entirely altered and the original character upon which it 

 was based wholly ignored. 



The two genera may be characterized in the following 

 terms : — 



A. The key-board of the stridulator placed 



upon the maxillary process of the coxa of 



the first pair of legs, the rasp or granular 



area in a slight depression on the adjacent 



surface of the coxa of the chela ; the lower 



surface of the bracliium with rows of 



piliferous pores and defined posteriorly by 



a ridge Scorpio (type africanus, 



L.).—Dis(r. 'Tropical 

 Ahica, S. Arabia. 



B. The key-board of the stridulator placed upon 



the coxa of the chela and the rasp upon 

 the adjacent area of the coxa of the first 

 pair of legs ; the lower surface of the 

 brachium without regularly arranged pili- 

 ferous pores and posteriorly more convexly 



rounded Palamnmis (type Petersii, 



Th..).—Dikr. Oriental 

 Region (Bombay to 

 Borneo). 



I have noticed the position of the stridulator in the 

 following species of Scorpio'. — africanus, Linn.; dictator^ 

 Poc. ; cavitnanuSj Poc. ; hellicosus^ L. Koch ; viatoris, Poc. ; 

 exitialis, Poc. ; and Gregorii^ Poc. : and I think there can 

 be no reasons for doubting that it will prove to be present in 

 Sc. africanus subfypiciis, Kraep. ; arahicus, Kraep. ; pallidus, 

 Kraep. ; and meidensis, Karsch ; of which the last-named, 1 

 doubt not, belongs to the exitialis-Y\ke forms of the genus, 

 and not to OpisthopJ/thalmus, as Kraepelin has suggested. 



As lor Wood-Mason's organ, it occurs in specimens that 

 I refer to the following speciesof Palamnceus: — scaler (Thor.) ; 

 Swamrnerdami {^ixn.) ; fulvipes {^oc\\) ; megacephalus (Koch); 

 ccpsa?- (Koch) ; hengahnsis {Koc\\)\ Phipsonii^o^:..) ; latimanus 

 (Poc.) ; gravimanus (Poc.) ; indicus (Linn.) ; spinifer (Hempr. 

 & Ehrb.) ; ThorelUi. Poc. j liophysa, Thor. ; and horneensis, 

 Thor. 



It is also worth bearing in mind that the presence of these 

 organs will serve as an additional character for separating 

 Scorpio and Palamnceus from Opisthophthalmus and Hetero- 

 metrus. 



