1908.] GENUS OF AMPHIPOD CRUSTACEA. 391 



Young (PL XIX. fig. 10). — The proportions of the first five 

 joints are the same as in adult, but the hand diflfers somewhat. 

 It is held in the normal position, not inverted, tliough showing a 

 tendency to curvature. It is more ovoid in shape, produced 

 posteriorly beyond the palm limit, which is defined by a spine 

 opposed to the tip of the claw. Close to this spine, one small 

 tooth can be seen, the distal one of the small series. None of the 

 joints is furnished with set* except only the claw, which has 

 two minute ones at the tip. 



The hand is much larger in the young in proportion to the 

 size of the animal than in the adult ; measured across the widest 

 part, in the yoimg it is 1"5 mm. to 7 mm. of total length ; in the 

 immature 2 mm. to 9 mm. total length; and in the adult 3"75mm. 

 to 26 mm. 



Second Gnathopod. Adult (PI. XIX. fig. 11 ; PI. XX. figs, 1, 

 2, 3, 4, ifc 5). The 2nd joint is long, broadest distally ; the 3rd nearly 

 as long as the second ; the 4th short, narrow proximally, rounded 

 posteriorly with the posterioi- margin twice as long as the 

 anterior ; the 5th is nearly as long as the third ; the 6th is 

 broadly ovate, only half the length of the fifth, very narrow at 

 the base, but expanding laminarly on both sides ; the 7th or claw 

 is minute, nearly hidden under the long setae, and situated in the 

 middle of the distal margin of the sixth. 



Setce,. — There are no setse on the 2nd joint ; one small one 

 distally on the 3rd ; a little fringe of fine setse on the posterior 

 margin of the 4th, with three small spines across the distal angle ; 

 the 5th is furnished with two dense masses of very delicate, 

 hyaline hairs (fig. 5), one mass covering the anterior surface and 

 the other the posterior. At the anterior angle is a fringe of 

 12 strong, flexible sette, reaching to the distal margin of the 

 succeeding joint. Each seta consists of a stout shaft, finely and 

 transversely serrated for half its length, with a slender flagellum 

 (see fig. 4). Anothei' cluster of these setae, shorter in length, 

 appears at the posterior distal angle and extends partway under 

 the joint. These two kinds of sensory setfe, the " hyaline " and 

 the " jointed," are peculiar to the 5th and 6th joints of this 

 gnathopod. The 6th joint is nearly covered with the hyaline hairs, 

 with two thick tufts on the distal angles ; the posterioi- angle 

 has a small group of the jointed setfe ; while on the anterior 

 angle is a cluster of about 50, the longest being twice the length 

 of the joiirt. On the distal margin are two small clusters of the 

 stiflF, slightly curved, seirated bristles peculiai- to this joint 

 (fig. 3J. They are placed one on either side of the claw, the 

 group on the upper surface of the joint containing three bristles 

 and that of the inider side four ; iDetween them is the denticu- 

 lated groove into which the claw fits. Bordei'ing this groove are 

 6 stout sensory spines, three on each side, with their thick shafts 

 embedded for two thirJs their length, and their large flagella 

 reaching beyond the apices (fig. 1). The curved under surface 

 of the claw is also covered with minute denticles. It is provided 



