144 U.S. NATIONAL MUSEUM BULLETIN 23 6 



1,4, 5, and appendicular seta small, setae 2 and 3 lengthened and 

 thickened, especially the 2nd. None of setae swollen at base. In- 

 ternal and external margins of furcal rami with some dispersed 

 spinules (fig. 516). 



Antennules very short, 5-segmented, 3rd segment long, with small 

 apical conical process, bearing aesthetasc and 2 setae. Setation 

 represented in figure 51c. 



Antenna (fig. 51c?) with 3-segmented exopodite, segment 2 very 

 small. There are 2 setae on segments 1, 1 on segment 2, 4 on segment 

 3. Allobasis with strong internal seta which appears to have been 

 overlooked by Sars. 



Mouth parts in complete agreement with Sars' description and 

 figures (1906, p. 140, pis. 85, 86); they will not be described in detail 

 here. Leg 1 (fig. 526) with 1 -segmented endopodite and 3-segmented 

 exopodite. Coxa with spinulose internal tubercle. Basis with 

 strong internal and external spine; insertion of external spine and 

 of exopodite fringed with spinules. 1st exopodal segment styliform, 

 5 times as long as broad, seta at external margin slightly above 

 middle of that margin. Segments 2 and 3 small, jointing indistinct. 

 2 hooked spines of very unequal size on apical segment. Endopodite 

 half length of 1st exopodal segment, with 6 appendages: fine seta at 

 external border and 5 spiniform setae dispersed along apex and in- 

 ternal border. In addition, there is an internal swelling on the 

 endopodite set with spinules. 



Legs 2 to 4 with 3-segmented endopodites and exopodites. The 

 structure of these legs appears clearly from figures 51e, b2c,d; the setal 

 formula is : 



endopodite exopodite 



leg 2 1. 2. 221 1. 1. 223 



leg 3 1. 2. 321 1. 1. 323 



leg 4 1. 1. 221 1. 1. 323 



In the structure of the legs also there is complete agreement with 

 Sars' description and figures (loc. cit.). 



Exopodite of leg 5 (fig. 52e) small, rounded, about as long as baso- 

 endopodite. External lobe of baso-endopodite well developed, slender, 

 with fine seta. Exopodite with 5 setae, median seta fine. Baso- 

 endopodite with 5 setae: group of 2 external and 3 internal setae. 

 Color completely faded, greenish, no eye or pigmented spot visible. 



Remarks. — The present female specimen agrees perfectly with 

 Sars' description and figures (1906) of northern representatives of 

 this species. Lang gives the length of female specimens as being 

 from 0.63 to 0.9 mm.; these measurements must be based chiefly 

 upon the Atlantic specimen since Diarthrodes nobilis has its main 

 area of distribution in tropical, subtropical, and boreal parts of the 



