368 



CEYLON PEARL OYSTER REPORT. 



(b) ov. ? 

 75 

 0-17 

 0-86 





 

 

 

 

 

 

 1 

 

 1 



Description : (<,) ad. g . 



C.l 10-25 



Rostrum L-S-C.L . . 0"20 



C.b.-i-C.l 078 



Anten.flag.l. -=-C.l. . . 0-83 



Post. bord.C.-r C.l. . . 0-32 0'46 



Arm.L-T-C.1 0-78 0-51 



Wrist! H-C.l. . . . 0-59 , 0-37 

 H.l. (up. bord.)-=-C! . 0-73 0-37 



H.b.^C.1 0-36 0-11 



F.l.-r-C.l 0-54 0-40 



W.L.l.lsch.l.T-C.1. . . 0-39 0'34 

 Merop!-=-C! . 2-10 | 1*46 

 Carp.l.-4-C.l. . 0-93 | 070 

 Prop!-=-C! . 2-00 1-49 

 dact.l.-rC.L. . 

 The division between carapace and rostrum is taken to be a line uniting the 

 anterior borders of the orbits ; C.b. = a straight line uniting points above base of 

 W.L.I of either side, which is the region of greatest breadth; posterior border of 

 carapace = a straight line uniting points behind the lateral tubercles of the posterior 

 border; cheliped segments and segments of W.L.2 are measured along upper edge. 



Description of Ovigerous Female (/). Carapace sub-triangular, the postero-lateral 

 angles well rounded, and the posterior border concave. The rostral lobes appear to 

 the naked eye to be united to form a single short median dorsally grooved and bluntly 



pointed projection which reaches for- 

 ward about as far as the distal end 

 of the first joint of the antennal 

 flagellum. The carapace is narrowed 

 laterally behind the eyes. There is a 

 post-hepatic constriction due to the 

 branchio-cardiac groove. The greatest 

 breadth is in the region above the first 

 pair of walking legs. The regions 

 of the carapace are distinct. The 

 carapace armature consists of (1) 

 tubercles, (2) straight hairs, (3) 

 hooked hairs. The general surface beneath the hairs is smooth ; of the tubercles 

 two at once attract the eye a large conical gastric one and a still larger one 

 on the cardiac region. The tubercles are in detail : 3 gastric, arranged in form 

 of a triangle, of which the two anterior ones, forming the base, are inconspicuous, 

 while the median posterior one is that already mentioned 1 cardiac (median), the 



Fig. 3. Achceus dubia, n. sp. 



