284 CEYLON PEARL OYSTER REPORT. 



length equal to the 2nd joint. Furcal rami short and wide, ahout as broad as 

 long. 



In washings from Muttuvaratu pearl oysters. 



The proportional lengths of the joints of the anterior antennae, and the long and 

 narrow 5th feet, distinguish this species from any of the others. 



Hersiliodes dubia, n. sp. Plate III., figs. 18 to 27. 



Length, male 1 '8 millims. ; female unknown. 



Cephalothorax quadrate in form, composed of 5 segments. Anterior antenna? 



6-jointed, and all clothed with non-plumose setae ; the proportional lengths are as 



, .. 1. 2. 3. 4. 5. 6. 



follows : 



8. 6. 5. 3. 4. 8. 



Posterior antennae 4-jointed, the basal joint equalling in size the 3 following. 



Mandible with 2 horizontal plumose projections and 2 plumose seta?. Maxilla 

 with 3 terminal spinous setae, and 4 on the outer side, 2 of them plumose. First 

 maxilliped 2-jointed, the apical joint terminating in a strong curved claw and a 

 plumose spine on each side. Second maxilliped 2-jointed, the basal one with a rounded 

 papilla ; the hand angularly curved on outer side, terminating in a long rounded claw 

 bluntly rounded at apex, and having on under side 3 spinedike setae. 



First 4 pairs of natatory legs 2-branched, each having 3 joints with the edges 

 mostly clothed with fine hairs. Fifth pair each consist of a quadrate joint with 

 3 strong spines and a few hairs and setae at base. Abdomen rather shorter than the 

 cephalothorax, 5-jointed, the genital segment very large, nearly square, and having 

 hooked posterior lateral terminations. 



Furcal rami linear, about 4 times as long as broad, with a small spine on each 

 outer side and terminating in 3 setae of unequal lengths. 



One specimen only, a male, was taken in the Suez Canal. 



This species agrees, in most particulars, with Cantj's Hersiliodes. Canu, however, 

 gives 7 joints in the anterior antennae, although his careful drawing of H. pelseneeri 

 shows only 6 joints. It is evident that the species comprising the genus Hersiliodes 

 undergo considerable changes in their various ecdyses, and in the absence of an adult 

 female we can only provisionally place our species in this genus. 



Family: ONCEID^E. 

 Oncea venusta, PmLirpi. 



Oncea media, Giesbr, 



Oncea minuta, Giesbr. 



Oncea mediterranea, Glaus. 



All the above were generally distributed over the entire voyage. 0. media was 

 found only once about Ceylon, viz., at Mudalaikuli Paar. 0. mediterranea occurred 



