276 CEYLON PEARL OYSTER REPORT. 



(B) Elasmopus dubius, n. sp. Plate V., figs. 35. 



One male from pearl oysters, East Cheval Paar, 8th November, 1902. 



Body smooth, without dorsal teeth. 



Head : ocular lobe rounded, with an acute, re-entering angle and a narrow rounded 

 lobe below, as in E. rapax. Eyes large, wide-oval, dark. 



First 4 side-j:>lates about as deep as the segments. 



Upper antennas of moderate length ; the 1st joint as king and twice as thick as 

 the 2nd and about one-third longer than the 3rd, Flagellum 16-jointed, a little 

 shorter than the peduncle. Appendage 2-jointed, the 2nd rather the longer, a little 

 longer than the 1st joint of the flagellum. 



Lower antennae reaching the end of the peduncle of the upper, 2nd and 3rd joints 

 subequal ; flagellum 8-jointed, rather longer than the last joint of the peduncle. 



Mouth organs as in E. rapax. 



Maxillipeds as in E. rapax. 



First gnathopods : side-plates irregularly rhomboidal, the anterior angle rounded, 

 with a few setae on the lower margin. First joint about as long as the next 3 ; wrist 

 rather shorter than the hand, the hind margin densely setose; hand with the palm 

 rounded off into the hind margin, but defined by a spine (fig. 35. gn. 1 ). 



Second gnathopods : side-plates rounded below, not reaching half-way down the 

 1st joint ; this is longer than the next 3 ; 3rd joint produced behind in a narrow lobe 

 with 5 or 6 setae ; wrist very short and wide, hind margin with a dense tuft of seta?. 

 Hand nearly twice as long as the 1st joint, margins subparallel and subequal, the 

 front slightly the longer and smooth, except 2 or 3 setules ; the hind margin has 9 or 

 1 fascicles of seta? and ends in a strong tooth which defines the palm ; this is trans- 

 verse, not oblique, narrow, with a central tubercle ; the hinge of the dactylus is as 

 wide as the palm. Dactylus peculiar, bulbous at the base and very strong, with a 

 curved blunt point which meets the defining tooth of the hind margin (fig. 35. gn.'-). 



First and 2nd pera?opods almost as long as the 4th and 5th ; 1st joint narrow, as 

 long as the 3rd and 4th together; 4th and 5th spinous on the hind margin. 



Third perseopods wanting. 



Fourth and 5th peraeopods subequal and similar, stout; 1st joint five-sixths as wide 

 as long, hind margin serrate, front spinous ; 3rd joint produced downwards in, front ; 

 otherwise subequal to 4th and shorter than 5th; all the joints spinous. Dactyli 

 strong (fig. 35. pp. 5 ). 



First uropods : rami subequal, shorter than the peduncle ; all spinous. 



Second uropods short and stout ; outer ramus shorter than the inner and subequal 

 to the peduncle ; all spinous. 



Third uropods wanting. 



Telson reaching beyond the middle of the 2nd uropods, divided nearly to the base, 

 the divisions notched at the tip with a long and a short spine in each notch. 



Length 5 millims. 



