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anal segment shorter than the 2 preceding segments combined. Caudal rami 

 very small, being much shorter than the anal segment, and scarcely more than 

 twice as long as they are broad; seta of outer edge attached a little in front 

 of the middle; innermost apical seta slightly exceeding the outermost in length. 

 Antennas and oral parts on the whole resembling in structure those in O. coni- 

 fera. Posterior maxillipeds, however, somewhat less strongly developed, with 

 the propodos oblong oval in form ; dactylus somewhat shorter than the pro- 

 podos and finely denticulated along the inner edge. Natatory legs with the 

 rami comparatively more slender than in O. conifera, and the spines of the 

 'outer ramus less strong. Last pair of legs with the free joint much smaller 

 than in that species, not cylindrical, but rounded oval in form. Ovisacs of 

 moderate size, extending about to the end of the anal segment, and oval 

 in form. 



Male much smaller than female, with the anterior division of the 

 body narrower and wanting the dorsal hump. Tail comparatively shorter, with 

 the genital segment very large and tumid. Anterior antennae with the joints 

 of the terminal part imperfectly separated. Posterior maxillipeds resembling in 

 structure those in female, but of somewhat larger size, with the dactylus longer 

 and quite smooth. 



Body in both sexes, pellucid, with a fainte yellow or orange tinge. 



Length of adult female scarcely exceeding 0.70 mm.; that of male 

 0.40 mm. 



Remarks. The above described species has been previously identified 

 by the present author with O. conifera Giesbrecht, which it ressembles in the 

 presence on the 2nd trunkal segment in the female of a hump-like dorsal 

 prominence. Having however now had an opportunity of examining Gies- 

 brecht's species, I find it to differ in some points so markedly that I am led 

 to the conclusion, that it is specifically distinct from the form here treated of. 

 I have recently examined another form from the Malayan Archipelago, the 

 female of which has a quite similar dorsal hump, and which on this cause 

 has been identified by Clewe with O. conifera; but which, on a closer ex- 

 amination, has turned out to be a very distinct species, different both from 

 that species and the one here described. The above-mentioned dorsal hump 

 cannot therefore be regarded as a character exclusive of O. conifera. The 

 latter is a much larger and more robust species than the one here treated of, 

 and moreover differs conspicuously in the relative size of the genital segment 

 in the female, as also in the much fuller development of the last pair of legs, 



