MOEPHOLOGT OF THE PBDIPALPI. 21 



of the carapace, beBind which come nine band-like sclerites, the 

 body ending in the three narrow, cylindrical sclerites of the tail. 

 The second to eighth sclerites show depressions which indicate 

 the points of attachment of the dorso-ventral muscles. On the 

 ventral surface the carapace is bent over in front for a sbort 

 distance. This infolded part is marked by a strong median 

 longitudinal ridge which helps to separate the bases of the 

 chelicerae. 



The cJielicercB (PL lY. fig. 13) are two-jointed, the distal joint 

 being claw-shaped; it is strongly articulated to the first joint 

 at the upper edge and folds down across its end, tbe point 

 reaching to the lower edge. The proximal joint is roughly 

 rectangular, as seen from the side, the length being about twice 

 the breadth. In section the shape is an elongated oval, the 

 long axis being dorso-ventral in direction. The surface of this 

 joint is smooth except toward the distal end, where it is furnished, 

 on the inner side, with a thick crop of hairs. The chelicerae are 

 not articulated to the rest of the skeleton, but attached by thin 

 membrane to the thick membrane which forms the front of the 

 eephalothorax in such a way as to be capable of being retracted 

 for more than half their length (PL III. fig. 1). 



The second pair of appendages are very powerful, and consist 

 of six joints. In the middle line the first joints are fused 

 together for about two thirds of their length, thus completely 

 shutting in the mouth behind. Being thus fused, the first joint 

 can no longer function as a jaw, as it does in the Scorpions, 

 and the biting-function is consequently taken on by the second 

 joint. Anterior to the point where the fusion ceases, the inner 

 surface of the first joint has an organ corresponding to what has 

 been termed the pseudotrachsea in Scorpions and Phalangidce*, 

 and which Gaubertf has shown to exist in Plirynus. This organ 

 consists in Thelyphonus (PL lY. fig. 12,p.s.t.) of a trapezoidal area 

 of thin skin closely covered with hairs. Except along the ventral 

 margin the hairs are stout, with a well-marked central cavity, 

 and covered with minute secondary hairs which give them a 

 feathery appearance. Along the ventral margin is a ridge 

 bearing stronger hairs, which, however, have not the feathery 

 structure. At the anterior end is a small chitinous plate covered 

 with short spines and bearing one or two long bristles which are 



* Macleod, Eull. de I'Acad. Belg. vol. viii. 



t Gaubert, Ann. Sci. Nat. ser. 7, vol. xiii. p. 140. 



