XI.— THE FAUNA OF BRACKISH PONDS 

 AT PORT CANNING, LOWER BENGAL. 



Part V. — Definition of a New Genus of Amphipoda, and 

 Description of the typicai. Species. 



By the Rev. Thomas R. R. Stebbing, M.A., F.R.S., F.L.S., F.Z.S. 



AMPHIPODA gammaridea. 



Family GammaridcB. 



1906. GammaridcB, Stebbing, in Das Tierreich, Lieferung 21, 

 pp. 364, 729. 



Quadrivisio, n. g. 



Eyes four, separate, well developed. First antennae the shorter, 

 with elongate accessory flagellum. Upper lip with rounded distal 

 border. Mandibles with slender palp, the second joint longer than 

 the first, but not longer than the third. First maxillae having i he 

 inner plate fringed with numerous setae, the second joint of the palp 

 large. The second maxillae fringed along the inner margin of the 

 inner plate. Gnathopods subchelate, first pair small, second very 

 large in the male, small and differently constructed in the female. 

 Third uropods much produced, the rami subequal, foliaceous. Tel- 

 son smaU, cleft to the base. 



By the character, though not by the number, of its eyes, the 

 species for which this genus is instituted, appears at present to be 

 unique. In the Ampeliscidae four eyes are common, but they are 

 externally sunple. In the Synopiidae and Tironidae there are spe- 

 cies with four eyes, but in both cases the lateral pair are minute, 

 and in Synopia the dorsal pair coalesce at the top of the head. In 

 Hirondellea trioculata, Chevreux, the nmnber is definitely only 

 three, the dorsal breadth of the head being occupied by one large 

 oval eye, not as in the present instance, finding room for two well 

 separated organs of vision to supplement the fully developed lateral 

 pair. 



In other respects the genus has characters already known in 

 the family Gammaridae, though not in precisely the same combina- 

 tion. The third uropods resemble those m Megaluropus, Norman, 

 a genus in several other features very distinct from the present. 

 Sexual difference is here marked by the smaller size of the female 

 and characters affecting the antennae as well as the gnathopods. 



