ARTHROPODS. 297 



DIAGRAM XIV. 

 Arachnoidea. 



The figure of a scorpion shows the under surface : — ( i ) the chelicerae, 

 (2) the pedipalps, (3-6) the walking-legs, 0. the operculum, p. the 

 pectines, pr. a. the prse-abdomen, with four pairs of respiratory aper- 

 tures, p. a. the post-abdomen, with a terminal sting (st. ). 



The figure of the king-crab (after Packard) also shows the under 

 surface: — (i) the appendages in front of the mouth, (2-6) the walking- 

 legs, o. the operculum, «. the abdomen, g. the appendages with gill- 

 books. 



In the centre of the diagram, the under side of the garden spider 

 (Epeira) is shown (after Vogt and Yung) : — c. the chelicerse, pp. the 

 palps, d. parts often distinguished as jaws, 1-4 the walking-legs, rep. 

 and p. s. the openings of the reproductive ducts and pulmonary sacs, 

 an. the anus, sp. the opening of the spinnerets. 



In the right upper corner is a section of a chambered trachea, pul- 

 monary sac, or lung-book (Z. bk. ) (from Lang, after Macleod). The 

 outer skin {sk.), the aperture or stigma {st.), the air-chamber {a. ch.), 

 the tracheal cavities {(r.), the bridges {br.) uniting the walls of adjacent 

 tracheae, are marked. 



To the left is the web of a garden spider, showing (a) the first spiral, 

 (b) the second spiral, (c) the radial filaments. (From the Standard 

 Natural History. ) 



