438 PROCEEDINGS OF THE NATIONAL MUSEUM. voi. xxxiii. 



These latter are broad but short and occupy nearly the whole of the' 

 free sides of the abdomen; each is armed with four large setse, one 

 near the anterior margin and the other three bunched together on 

 the posterior margin. 



Both joints of the first antennae are well armed with seine, some of 

 which are much longer than usual; neither joint has such bushy setae 

 as portrayed by Steenstrup and Liitken, but they are much better 

 supplied than usual. There is a circular adhesion pad behind each 

 antenna close to the margin of the carapace. 



The second antennae arise near the base of the mouth-tube, are of 

 the usual shape, and end in a powerful claw, strongly curved. The 

 second maxillae have a stout basal joint, while the terminal spine is 

 long and slender; the same is also true of the hrst maxillipeds, whose 

 slender claw is nearly as long as the terminal joint. Close to the base 

 of the claw can be seen the spindle-shaped fuiger mentioned by Steen- 

 strup and Ltitken as going out at right angles to the posterior border 

 of the terminal joint, and a group of spines between the finger and the 

 terminal claw and around the base of the latter. The long terminal 

 claw is also fringed with fine spines as in their specimens. 



The second mixillipeds have a single knob on the ventral surface 

 of the swollen basal joint, and a pair of pincher-like knobs on the 

 terminal joint. wSteenstrup and Liitken give this appendage armed 

 with a long claw instead of the pincher-like jaws, but this is no more 

 of a variation than is commonly found in other species of this genus. 

 As noted on page 330 the second maxillipeds of the males of alatus are 

 sometimes furnished with claws and sometimes with pincher-like 

 knobs. 



The arrangement of the spines and setae on the swimming legs is 

 as follows: First basipod, 2 spines: exopod, 1, 0; 3, IV: endopod, 

 0, 0; 0, III: second l)asipod, 1 seta: exopod, 1, I; 3, A ; endopod, 

 0, I; 0, VII: third basipod, 1 seta: exopod, 1, 0;1, V: endopod, 

 0, I; 0, IV: fourth })asip()d, naked: exopod, 2, IV: endopod, 0, IV. 



Total length, S.2 mm. ; length of carapace, including posterior 

 lobes, 3.8 mm.; width of same, 3.2 mm.; length of free thorax, 

 2.8 mm.; length of genital segment, 2.1 mm. 



Color (preserved material) a uniform yellowish brown, much 

 darker on the genital segment and abdomen, but without pigment. 



{borealis, northern, all the specimens having come from the far 

 north.) 



The U. S. National Museum Collection contains a single specimen 

 of this species Cat. No. 32789, U.S.N.M., which came from an 

 Alaska collection made by Dr. W. H. Dall. The size of this male 

 and of those recorded by Steenstrup and Liitken, which were 11 

 mm. long, indicates that the female must also be larger than the 

 ones already described. 



