COPEPODA FROM IFALUK ATOLL 149 



5th thoracic somite scarcely visible from above, represented by very 

 narrow strip in front of genital somite. Genital somite resulting 

 from fusion of abdominal somites 1 and 2; line of fusion visible in 

 dorsal view but scarcely in lateral aspect. Genital somite with almost 

 straight lateral walls, tapering slightly distally. In the present 

 specimen the abdominal somites are very strongly contracted (fig. 

 536) but in the specimen from locality 425 the genital somite is 1}^ 

 times as long as the 3rd abdominal somite, this again slightly longer 

 than 4th, while the anal somite is very short (fig. 54a). Spinules 

 occur only at the dorsolateral surface of the 3rd abdominal somite 

 and at the insertion of the furca on the anal somite. Anal flap not 

 visible dorsally. 



Furcal rami parallel, rami as long as broad or slightly broader, 

 with 5 marginal setae and 1 appendicular seta (fig. 53d). Setae 1, 4, 

 and appendicular seta fine and short, seta 5 very short and spiniform. 

 Setae 2 and 3 lengthened and thickened, especially 2nd, which reaches 

 length of body. Both setae 2 and 3 are swollen slightly at base. 

 In addition to setae there are some spinules on the external wall of 

 each ramus. 



Antennules (figs. 53c, 546) 8-segmented, reaching halfway length 

 of cephalothorax. Setation and length of segments can be taken 

 from figure 53c. The 4th segment is not lengthened but has a conical 

 process bearing an aesthetasc and 2 setae. 



Antenna and mouth parts agree completely with previous descrip- 

 tions, particularly those of Sars (1905, p. 126, pis. 77, 78, fig. 1) and 

 will not be described or figured. Exopodite of antenna 3-segmented; 

 number of setae on these segments is 2, 1, and 4, respectively. 



Leg 1 (fig. 55a) with 3-segmented exopodite and endopodite. Coxa 

 with spinulose tubercle at external margin. Spine at internal margin 

 of basis strong, at its base with a fringe of spinules; spine at external 

 margin smaller, setiform. Spinules also occur near insertion of 

 endopodite on basis. Exopodite % length of 1st endopodal segment. 

 2nd exopodal segment 2K times as long as wide, with seta at internal 

 and spine at external margin. 3rd exopodal segment notably small, 

 with total of 5 appendages. Seta on 1st endopodal segment inserting 

 halfway along that margin, segment styliform, 4)^ times as long as 

 wide; external margin spinulose. 



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

 ticulars of these legs can be taken from figures 54c, 556,c; the setal 

 formula is : 



endopodite exopodite 



