260 CEYLON PEARL OYSTER REPORT. 



margin ; 3rd similar in form, but narrower and without the teeth ; 4th rather smaller, 

 with a shallow emargination on the lower margin ; remaining side-plates comparatively 

 small. 



Upper antennae rising from the point of the hood-like projection of the head, the 

 peduncle reaching to the end of the 2nd joint of the lower antenna? ; the 1st joint 

 much wider and rather longer than the 2nd, which is subequal to, but thicker than, 

 the 3rd. Flagellum 6-jointed, about as long as the last 2 joints of the peduncle. 



Lower antennas apparently originating behind the articulation of the 2nd gnathopods 

 to their side-plates ; the 3 peduncular joints subequal. Flagellum 3-jointed, half as 

 long as the last joint of the peduncle. 



Mouth organs obsolete, except a pair of minute processes called by Stebbing "oral 

 laminae " in the form of 2 small plates below the head, which are probably rudimentary 

 mandibles. 



Maxillipeds : no inner or outer plates ; palp apparently 5-jointed, including the 

 dactylus, the joints subequal, but the 3rd rather the shortest and widest with a long 

 spine on an angular projection on the inner margin ; the 4th rather the longest and 

 narrowest ; the dactylus is slender, curved, and as long as the 4th joint. 



First gnathopods very small and perfectly chelate ; the 1st joint as long as all the 

 rest, narrow at the top and widening suddenly a little below the middle ; 2nd joint 

 rather shorter than the 3rd ; this takes the place of the wrist, which is obsolete, and 

 supports the hand ; this has the hinder part produced in an immovable finger as 

 long as the rest of the hand, the end curved upwards and rounded at the point. The 

 dactylus is a little shorter than the immovable finger and curved downwards, the 

 ends of the fingers crossing ; to conrplete the resemblance to the chelipede of a crab, 

 the inner margin is furnished with blunt teeth. The entire limb extended is slightly 

 longer than the hand of the 2nd gnathopods (fig. 18. gn. 1 ). 



Second gnathopods : the 1st joint conspicuously articulated to the middle of the 

 side-plate, as long as the hand, curved and widening distally ; 2nd joint with a wide 

 groove to receive the base of the wrist ; 3rd joint oval, pointed, and articulating with 

 the wrist at about one-fourth of its length from the base ; wrist produced in a curved 

 and pointed process almost as long as the hind margin of the hand, denticulate on 

 the inner margin near the base. Hand widest near the base, front margin convex, 

 hind rather concave beyond the middle. Dactylus about two-thirds of the length of 

 the hand and meeting the end of the carpal spur, convex and denticulate on the 

 proximal half (fig. 18. gn. 2 ). 



First and 2nd perseopods : side-plates wide and irregularly angulated below ; 

 1st joints reaching below the side-plates, widening distally. 



Third and 4th perseopods : 1st joint expanded and rounded behind. 



Fifth perseopods: 1st joint expanded behind with the margin subangular above 

 and divided by a series of short transverse ridges into 1U or 11 irregularly angulated 

 spaces (fig. 18. pp. 5 ). 



