52 CEYLON PEARL OYSTER REPORT. 



rounded lobe fitting into the emargination." Norman says ot the head in J. dollfusi 

 " the anterior margin is emarginate, and in front of this the buccal organs are 

 conspicuously projected," but his figure also shows the rounded lobe in the emargina- 

 tion. The figure of J. dollfusi shows the pleon more sharply contracted towards the 

 apex and the sides more deeply serrate than is the case with the present species. 



The eyes are not large, not dark, placed near the front angles of the head. The 

 first antennse have a broad basal joint, seemingly denticulate at the front corners. 

 The second joint is much shorter and much narrower, the third smaller than the 

 second, and the two remaining joints very insignificant, but tipped with two long 

 filaments. 



The second antennae are of the typical form, seemingly with three short basal 

 joints, followed by the characteristic large dilated joint with thin outer margin 

 slightly crenulate, not strongly as in J. dollfusi; to this succeeds a much smaller, 

 apically expanded joint, helping to form a double geniculation. The five remaining 

 joints, perhaps, constitute the flagellum, but the first, which is very far the largest of 

 them, has usually been accounted the terminal joint of the peduncle. It is, however, 

 not very usual for the penultimate joint of the peduncle to be shorter than the joint 

 preceding as well as the joint following it. 



The upper lip has a rounded distal margin. The mandibles have the cutting edge 

 cut into five teeth, eight spines in the spine-row, the three-jointed palp very small. 

 The first maxillae have three short spine-like seta? on the inner plate, and nine to 

 eleven spines, mostly denticulate, on the outer plate. The second maxilla? are 

 notable for the shortness of the inner plate ; each of the three plates carries four 

 apical seta?. The maxillipeds have a very large second joint with extremely broad 

 plate, the distal margin slightly and irregularly crenulate with a gentle curvature or 

 sinuosity, distinct from the quadrate character displayed in J. dollfusi. The coupling 

 hooks are two. The fourth joint is distally produced on the inner margin, the sixth 

 joint is very narrow and the seventh minute. 



The limbs of the peraeon differ but little, the fourth joint being shorter than the 

 third, fifth, or sixth. The finger has two conspicuous nails and one that is 

 inconspicuous. 



The operculum of the pleopods in the female is broadly rounded for nearly two- 

 thirds of its length, and then contracts to a narrowly truncate apex carrying four 

 setules. It does not show marks of a longitudinal or a transverse suture, such as are 

 said by Dr. Chilton to be indistinctly visible in his specimen. 



The uropods fill the emarginations of the pleon. The peduncle is more strongly 

 serrate on the inner than on the outer margin. The inner ramus is hook-like ; the 

 outer, which is even smaller than the inner, carries a bunch of setae. 



Length 2 millims. Nicolet gives 2 lines for the length of his specimen ; Chilton 

 about 2 '5 millims. for his. 

 Locality : Gulf of Manaar. 



