266 CEYLON PEARL OYSTEE REPORT. 



First and 2nd gnathopods almost alike, the wrist as long as the hand, which is 

 subtriangular, the palm almost rectangularly transverse (fig. 24. gn. 1 ). 



Perseopods as in D. spinosa, except the last pair, which have the 1st joint expanded 

 behind and coarsely and irregularly toothed or serrate (fig. 24. pp. 5 ). 



Telson divided nearly to the base; the divisions truncate at the tips, the outer 

 margin acutely produced, then a spine and 4 minute spinules (fig. 24. t.). 



Very near D. spinosa, from which it differs in the more transverse palms of the 

 gnathopods, the coarsely serrate and expanded 1st joint of the last perseopods, and 

 the armature of the telson. 



Tritaeta, Bobck, 1876 (= Polycheria, Haswell, 1880). 



Tritaata antarctica, Stebbing* Plate IV., fig. 25. 



Polycheria temiipes, Haswell, ' Proc. Linn. Soc. N.S. Wales,' vol. 4. (For further remarks 

 on the synonomy of this species, see " Challenger Report," pp. 451, 512, 945.) 



Station XLIX., 7 specimens. Talaivillu Paul', 1. Length of ovigerous female, 

 3'5 milliins. 



I have no doubt that these specimens are identical with Mr. Stebbing's species. 

 It is a question, however, whether, owing to the different structure of the terminal 

 joints in the perseopods, this can properly be included in the genus Tritceta. In the 

 type, T. gibbosa (Bate), the clasping by these limbs is effected by the point of the 

 dactylus meeting the prominent hind margin of the carpal joint, and G. O. Saks, in 

 his definition of the genus, says that " the 2 outer joints are modified for grasping," 

 so that unless one may consider the dactylus as one of the 2 joints (in which case the 

 definition is insufficient as regards the type), it does not apply to T. antarctica, in 

 which the short dactylus and the somewhat expanded and transverse palm of the 

 propodos form the grasping part (fig. 25. pp. 1 ). Haswell's genus Polycheria might 

 be revived if thought desirable. 



This species exactly resembles T. gibbosa in two respects : its extreme dirtiness and 

 its habit of carrying the antennae flexed at a right angle from the 2nd joint of the 

 peduncle. 



Guernea, Chevreux, 1 8 8 7 1 (= Helleria, Norman, 1868J). 



In his definition of the genus Helleria, Canon Norman writes : " Superior 

 antennae . . . with secondary appendage " ; but his figure of the head and antennae 

 does not show one. Chevreux also, in his definition of Guernea, writes : " Antennae 



* ' Ann. and Mag. Nat. Hist.,' Ser. 4, 1875, vol. 15, p. 184, Plate XVa. 



t ' Bull, dc la Soc. Zool. de France,' vol. 12, 1887. 



| ' Ann. and Mag. Nat. Hist.,' December, 1868, p. 418, Plate XXII., XXIII. 



Canon Norman informs me that the words "with secondary appendage " are an accidental error, 

 Monsieur Chevreux no doubt took his description from Norman's. See also Stebbing, ' Ann. and Mag. 

 Nat. Hist.,' Ser. 6, vol. 5 (1890), p. 192. 



