530 FAUNA HAWAIIENSIS 



From the species of Orchcstia above discussed the present species is separated by 

 many particulars in addition to the minute distinction on which the genus Parorchestia 

 is founded. 



(/. The upper antennae extend along at least two-thirds of the last joint of the 

 peduncle of the lower antennae. The second joint of the peduncle is longer than the 

 first, the third as long as the first plus the second ; the flagellum of nine joints is as 

 long as the peduncle. 



The lower antennae are slender, the penultimate joint of the peduncle more than 

 twice as long as the preceding joint, and the ultimate as long as both of these together; 

 the flagellum of twenty-one joints is as long as the peduncle or rather longer. As 

 usual, these dimensions and numbers are subject to some variation. 



The upper lip appears to be rather wider and shorter than in Orchcstia, but no 

 tangible differences could be discerned in mandibles, lower lip, and the two pairs of 

 maxillae. The maxillipeds differ from those of Orc/iesfni platensis in having both the 

 inner and outer plates smaller, the first and second joints of the palp less expanded, 

 the third joint with less convex margins, as well as in possessing a distinct though 

 minute fourth joint ; also the spinules on the various joints are fewer and more 

 scattered, none being seen on the outer margin of the inner plate, while on the other 

 hand the outermost spine-tooth on its distal margin is exceptionally large. 



The first gnathopods are slight, the fourth joint having a sort of boss or distal 

 expansion of the hind margin ; the fifth joint widens gradually to the rounded distal end, 

 and the sixth is rather similarly expanded, the small finger not quite reaching the 

 extremity of the palmar margin, which is not at all oblique. 



The second gnathopods have the sixth joint massive, broadly oval, the palmar 

 margin oblique, not strongly convex, ending in a small groove or pocket, to receive the 

 apex of the finger. The inner margin of the finger is slightly irregular, at its base not 

 fitting exactly the palmar margin, while its apex has a membranaceous aspect as in 

 Orchcstia platensis. 



The uropods scarcely differ in any important particular from those of the above- 

 named Orchcstia, but the telson has a truncate apex, with a spinule at each corner, two 

 smaller ones in between them, and two on each side above them. 



Length 13 mm. 



Except in regard to the two pairs of gnathopods and the purely sexual characters, 

 the male and female have close resemblance. Dana's figures of the female are unfortu- 

 nately very poorly reproduced in the Catalogue of the Amphipodous Crustacea in the 

 British Museum, 1862, a work which might have been of extreme value, had the plates 

 been executed with sufficient care to make them trustworthy. 



