788 



CLASS V. ARACHNIDA. 



lateral angles 



11 



L2 



segments, and are inserted by narrow bases at the antero- 

 of the camerostome. The five succeeding pairs 



subserve the 

 4 n double func- 



tion of masti- 

 cation and 

 locomotion. 

 Their broad 

 bases of inser- 

 tion are pro- 

 duced intern- 

 ally into spi nose 

 masticatory 

 lobes, w h i c h 

 form the lateral 

 boundaries of 

 the extra-oral 

 space. In the 

 female the fcur 

 anterior loco- 

 motory limbs 

 ( 1 1 - V ) are 

 chelate, while 

 in the adult 

 male (t h e 

 young males 

 resemble the 

 females) the 

 first (II), (in L. 

 moluccanus and 

 L. longispiiKi 

 the first two 



II and III) end in curved claws. The fifth pair (VI) differs from 

 the others by the possession of a peculiar curved spathulate pro- 

 cess articulated to the outer aspect of its base, by its non-chelate 

 termination, and by the presence of a group of four broad im- 

 bricated spines, which are separately movable, at the distal end 

 of the antepenultimate segment. These are used in shovelling 

 back the mud or sand in which the animals live, and in propell- 

 ing them forward. The spathulate process recalls a crustacean 



Fia. 511. Ventral view of Limulus pulyphemusx i. 1 cephalo 

 thorax ; 2 abdomen ; 3 caudal spine ; 4 chelicerae ; 5-9 the 

 five legs ; 10 genital operculum (1st abdominal appendage) ; 11-15 

 branchiate appendages (abdominal appendages 2-5) ; 16 anus ; 

 17 points to the region of the mouth : 18 chilaria (7th cephalo- 

 thoracie appendages) (after Shipley and MacBride). 



