AMPHIPODA. 295 



Platophhun, Dana, L852. 



Platoplnum laeve ( Has well). Plate VII. , figs. 51. 



Dexiocerella lasvis, HASWELL, ' Proc. Linn. Soc, N.S. Wales,' vol. x., 1886, p. Ill, pi. xviii. 

 Cyrtopkiura liaswelli, Chevreux and De Guerne, 1888. 



Stations V, XL VII. , LVIIL, all in Gulf of Manaar. 



The first 5 segments of the mesosome with a median transverse depression, the 

 last segment and the first 2 of the pleon carinate, the carinas not produced behind. 



Head considerably longer than the 1st segment. Lower angle of the ocular lobe 

 bluntly rectangular. Eyes wide-oval, dark in the centre. 



Upper antennae about as long as the head and first 2 segments ; 2nd and 3rd joints 

 of peduncle subequal, the fiagelhnn the same length, 4-jointed in the females, 5-jointed 

 in the males, the 1st joint much the longest. Appendage about one-third of the 

 1st joint. The whole setose below. 



Lower antennae are longer and less setose in the male than in the female, the 

 2nd joint considerably shorter than the 3rd and subequal to the 3-jointed flagellum. 



First gnatbopods : side-plates rhomboidal ; 1st joint rather shorter than the next 3 ; 

 hind margin of the wrist almost straight, setose. Hand subtriangular, longer than 

 the wrist in the male, widest near the base, the palm occupying two-thirds of the 

 bind margin and defined by a group of spines. Dactylus barely reaching the palmar 

 spines ; a row of spines on the inner margin and an obscure denticulation on the outer 

 near the point, which has a secondary tooth, giving it a split appearance. In the 

 female the hand is proportionately shorter than in the male, being only about as long 

 as the wrist (figs. 51. gn. 1 ). 



Second gnatbopods, female (fig. 5J. gn. 2 ?): the whole limb short and stout; the 

 1st joint subequal to the next 3 ; 3rd joint produced behind to a point tipped with a 

 spine ; wrist triangular, cup-shaped, with spines round the margin, about one-third as 

 long as the hand ; this is widely oval, the palm about 3 times as long as the rest of 

 the hind margin, from which it is defined by a spine ; about 6 spines and 4 long seta? 

 "ii the palmar edge, and 4 marginal and 3 submarginal spines on the front margin; 

 dad vlus rather longer than the palm. In the male the hand is 4 times as long as the 

 wrist, about 3 times as long as the hand in the female and proportionately narrower; 

 the palm occupies nearly the whole of the hind margin, is defined by a small tooth, 

 and is spinous, with a few short setae throughout its length; there are 5 groups of 

 spines (l long and 2 short spines in each) along the front margin (tigs. 51. gn. 2 ). 



First and 2nd peraeopods : the 1st joint narrow and as long as the next 2; the 

 3rd joint expanded distally, the front margin suhangnlate ; 5th joint almost as long 

 as the 3rd and 4th ; all the joints spinous (fig. 51. pp. 1 ). 



Third penvopods : 1st joint with a projecting lamina behind narrowing distally; 

 3rd and 4th joints subequal, 5th nearly twice as long; dactylus strong (fig. 51. pp. 3 ). 



