50 CEYLON PEARL OYSTER REPORT. 



Janira (?) nana, n. sp. Plate III. (C). 



The general appearance agrees with that of Jaeropsis curvicomis, in company with 

 which the specimen was taken, but the segments of the peraeon are not so markedly 

 separated. The pleon is nearly circular, not serrate, with a small apical convexity, on 

 either side of which the uropods probably protrude. 



The eyes are pale orange coloured, differing from those of Iais pubescens by having 

 not two but thirty-eight components. 



The first antennae have a stout basal joint, the second much smaller, and the third 

 almost like a flagellar joint ; the flagellum is longer than the peduncle, its seven 

 joints unequal in length, all slender, the last tipped with a couple of long setae or 

 filaments. 



The upper lip is rounded, and seemed to be projected forward with the lower lip. 

 The mandibles have a prominent cutting-plate divided into five teeth, the accessory 

 plate on the left similarly divided, but bidentate on the right. The spine-row has 

 five or six spines. The molar is prominent, denticulate. The three joints of the palp 

 are subequal in length. The first maxillae have a slender inner plate, and nine, 

 mostly denticulate, spines on the outer. The outer and middle plates of the second 

 maxillae carry each three setae. In the maxillipeds the plate of the second joint is 

 rather large, with several plumose setae on the distal margin, and one hook on the 

 inner margin ; the third, fourth, and fifth joints are broad, the fifth having its outer 

 margin longer than the inner ; the sixth and seventh joints are narrow. 



The first gnathopods have the fifth joint much broader but not longer than the 

 sixth, which in closing down would reach much beyond the palmar margin. The 

 finger is much the same in all the known limbs of the peraeon, having a short trunk 

 with two distinct nails. The second gnathopods agree with the first and second 

 peraeopods in structure, but are longer, especially in the second, fifth, and sixth 

 joints ; the sixth joint is narrower than the preceding joint. 



The male operculum is composed of the first two pairs of pleopods. The first pair 

 are narrow and more or less tapering, but with a constriction below the middle. 

 They end in two pairs of overlapping shortly lanceolate lobes. The second pair are 

 semicircular, with a long sinuous almost filiform masculine appendix. 



Length 1*5 millims. Haswell's Stenetrium inerme is described as -^g-ths of an inch 

 in length. 



Locality : Gulf of Manaar. 



Jaeropsis, Koehler. 



1885, Jaeropsis, Koehler, 'Ann. Sci. Nat.,' se>. 6, Zool., vol. 19, Art. 1, p. 2. 



1886, Jaeropsis, Beddard, ' " Challenger," Isopoda, Reports,' vol. 17, p. 20. 

 1891, Jaeropsis, Chilton, 'Trans. New Zealand Inst.,' vol. 24, p. 267. 

 1893, Jaeropsis, Steebing, 'History of Crustacea,' p. 379. 



1899, Jaeropsis, H. Richardson, 'Proc. U.S. Mus.,' vol. 21, p. 857. 



