APPENDAGES OF LIMULUS 



219 



another across the mesial plane and forming the genital operculum, the 

 genital openings being situated on their posterior face. Appendages 

 IX-XIII are also plate-like structures very much like the genital oper- 



FlG. 98. 



A King- crab (Limultts), female. B, ventral view. I, Chelicera ; II-VI, walking legs ; 

 VII, chilarium ; VIII, genital operculum ; IX-XIII, respiratory appendages ; a, anus ; t, telson.. 



culum, differing from it, however, in that each carries on its posterior 

 surface an arrangement of thin flat plates, lying over one another like 

 the leaves of a bocik (Fig. loi, A). These glll-1)ooks are the breathing 

 organs of the Limulus, each leaf containing blood and possessing a very 



