SCORPIONS, SPIDERS, ETC. 



295 



the ventral surface of each of the next 4 segments there is a 

 pair of breathing-slits {stigmata), each of which opens into a 

 cavity containing a close-set series of gill-like leaves— the 

 " lung-books." All these structures are regarded as modified 

 appendages. 



Fio. 130. — Ventral view of Scorpion. 



The 5 narrow segments that, with the post-anal spine, 

 form the tail are more or less sculptured and faceted ; the 

 anus opens at the end of the 5th. None of these segments 

 has appendages of any sort. 



The first pair of cephalothoracic appendages, or chelicer(e, 

 are short and pincer-like, and are rather deeply embedded 

 between the second pair. The latter, or pedipalps, are large 

 prehensile organs composed of 6 segments, and resemble the 

 great " claws " of a lobster. The next four pairs are crawling- 



fibialspun pedal spur 



Fia. 181.— Leg of Scorpion. 



legs. Each leg (Fig. 131) is composed of 7 segments and 

 ends in a pair of claws. The coxse of the first two pairs of 

 legs are produced anteriorly into maxillary processes (Fig. 

 1 30) which form a threshold to the mouth. At the end of the 

 protarsus, or 6th segment of the leg, there is a spine, known 

 as the pedal spur ; sometimes two pedal spurs are present. 



